mixed signals/waning sex life

Here's the deal. Been dating a girl for almost 4 months. Haven't had sex in 3 weeks. :-/ She fell over me big time in the beginning. (a little clingy/needy) As time goes on, things mellowed down a bit. Her drive to have sex was 24/7 basically. She'd always flirt and act horny around me and talk about it and almost any conversation could end in some innuendo.
So time goes on, she gets the impression from her mom that I'm happy with how things are and I don't want anything to change. (translation: I'm not looking for a future with you) I never said or inferred that (at least in my mind I didn't) so we talked and got it straigtened out and she was happy and glad I had the same outlook and goals relatively that she does.

There's been lots of times she gets emotional and doesn't want to let me go and even cries saying "I feel like this is too good to be true. I don't want it to end and I worry all the time that i'll do something to drive you away like how my mom says I have to be happy around you or you'll get tired of putting up with High school drama and leave because you don't have time for that." or " I worry about what you'll do when you find someone better who comes along."

So she basically tells me that she has low self-esteem and wonders what I see in her. She tells me about always being the 3rd wheel in a group at school and feels good when anyone popular acknowledges her existence. I know this will change in time because when I did the HS bit (1996) I wanted to be liked by popular kids too. But in the real world, it doesn't matter one bit. You make or break yourself and everything starts over everytime you switch school, jobs, careers. And usually, most people don't really give a f'k who you are after school or what your "rep" is.

We had an arguement about that last week and she cried about it. It was basically me saying how when I give her a compliment, (I give her compliments at least once every time I see her but not ALL the time. I know that the more you do, the less impact they have. ) she just shrugs it off, but when some kid at school give her a good one, or a 6 yr old kid she babysits gives her a bad one (called her fat) she gets all emotional. But more often then not when I give her a compliment, she just says "thanks" and smiles but looks as though I told her it was cloudy with 20% humidity. (in other words, a neutral reaction)
When she cried she said that "It's like i'm trying to tell you but it doesn't come out right. It's like when people tell me something good, i'm glad to hear it but I don't think much from it, but when it's from you, I know it's real and it's hard for me to believe that someone can say something so nice to me and ACTUALLY mean it."

There's times she cuts down herself and I almost want to tell her to just shut to F up! I don't mind sarcastically cracking jokes about something silly you did or whatever, but when she insults herself about things that are NORMAL to a typical human being, it pisses me off. "Of course it's ok if you don't have the waistline of Kate Moss. It's fine that you have mixed blood that gives you a unique look. No, you don't look "weird" because you don't look like a straight "white" girl. No, there's nothing wrong with not having giant tits and YES i'm not just saying I like them to make you feel better. And YES, when I tell you something about you that I find beautiful/wonderful, it's because I REALLY do mean it!"

Why don't girls get this? If a guy SAYS something, and his ACTIONS follow suit, then where's the confusion? If I said I love you but smacked you, then yeah, there's a mix-up. If I gave you affection but went over and stayed with another woman, yeah there's something to be confused about. But not what i'm doing. What I say/do is cut and dry. No weird signals.

Of course I don't give everything about me away. I keep her on her toes but not in a bad way. I don't do anything mean to her except confront her about things that are important to me even if it bothers her. (like our talk we had in the car about her views on herself and me)

(continued below)

When it comes to our sex life. It used to be great. She wanted it more than I did! She'd be beggin for stuff practically. There were nights I wanted to go out and DO something and she wanted to stay at my place and just go at it! (nothing wrong with that though)

I enjoyed having sex with her and so did she. She even told me that I was the first guy she's been with who has "made love" with her as oppsed to just having sex. (I wasn't being all emotional and saying "Oh, I love you so much, you're so beautiful, you fill my life with sunshine..." come on now.)
I just gave HER attention/affection instead of just getting my rocks off (as opposed to other guys she's been with: never had a realationship last past 1 month before me) and it blew her mind to actually have sex with MENTAL/EMOTIONAL satisfaction along with physical enjoyment. (and after 2 months she finally had an orgasm during sex. (she said it was her first ever with a guy)

But now it's been 3 weeks since we've done anything. 2 of those have been medical related. 3 weeks ago she had her tonsils out. But it's a bigger deal at 18 then as a kid. She was on codine and prednisone and definatly not doing well so that's expected that sex is out of the question. (funny thing is 1 day after surgery she was so out of it and in pain but kept asking me if we could have sex for awhile when her parents were out. I did want her to feel better so....hehe)
So for about almost 2 weeks she was just hurting so bad and on meds and very moody. (prednisone can do that to you) The next week she was having her flow and after that switched from the pill to the ring. (MAIN reason was that she didn't want to have to worry about popping a pill every night AND she heard it was supposed to feel good to the guy. She's in this mindset that she HAS to please me and I think that's one reason why she does oral on me but secretly doesn't like it)

So she went on the ring and it messed with her BIG time. Irritation, swollen, in pain, cramping, moody. We tried having sex and it was impossible with the ring in. We took it out (safe to do for short times, and she was so irritated and swollen we couldn't have sex)
She kept it in for about a week and we both could tell it was driving her nuts so she threw it out. So we've abstained for about a month because she's allergic to latex and she hurt for at least another week from that. (and the hormonal chemicles were still in her system and messed with her mood. Crying all the time, couldn't sleep etc.)

So now she's back to normal. But i'm getting mixed signals. Sometimes she acts horny and then when I THINK that she'd like to fool around, she really doesn't. And the times she DOES want to, I didn't catch. Like this past weekend. Friday night I bring her to my place and we hang out. She's finishing the end of her flow and we're just chillin. She's cuddling up to me and I know she's very tired from work so I tell her that we're going to go lay down and take a nap together in the bed so we do. We talk quietly about this and that and I stroke her hair as she lays in my arms. She tells me "You're the only one I can be with that makes me happy. Everyone else makes me feel sad but you never do. (but we do have little arguements at times like everyone else) I'm so glad i'm with you." and she doesn't make any noise but I can see her crying in the dark. We laid there for awhile and when it was time to leave we got our shoes on and she started tickling me and messing with me so I took her to the ground and we started making out. Then she wished that she wasn't on her period and that we had time so we could f'k.

Saturday: She got up to run errands to get ready for prom next week. We talked beforehand and we agreed on seeing a movie later on. When I picked her up, she said that she had a headache but would still do something. She was out of it the whole time at the theater and didn't enjoy being there but liked the movie. Afterwards, it was too late to do anything else so we stopped for Wendys and ate in the car and talked about stuff. (had our arguement about her self-criticizing herself and worrying so much about other people's thoughts. I'm 26 she's 18 so our views are different)
She told me that she didn't really want to see the movie and hoped I could see that because she wanted to go to my place for sex. (well if she just TOLD me that I would've been happy to oblidge since it's been like a month without it so i'd love to get back in the game!)

Sunday I went with her and her family to visit other family in Indiana. We got back so late there was no time to even consider going back to my place for sex. She hinted that she was dissapointed because she hoped that we'd have time but didn't act like she was THAT upset about it. One time she was laying on my sleeping on the way home and slid her hands up the inside of my shorts and touched me for a moment and stopped. That was the only flirting I got from her but even around her family visiting she always wanted to be next to me wherever I was.

Getting to the point of all this.... Tuesday is her off day. I asked her on the way home last night if she wanted to meet up tuesday and we could spend so quality time together. *wink wink* she goes "Oh, I think i'm spending time with my friend Samantha." I said "I thought you saw her last tuesday when you were off work." she goes "I did but I hardly ever see her." I just thought whatever. First you're dying to have sex, then when you KNOW we have the opportunity to do something without a doubt, you pass on the invitation. Wtf?

She was all excited last thursday and said that she can't wait to go back on the pill so we can have sex. I told her "You do know that you're basically fertile for the first month until your body adapts to the chemicles." she was like "what?....are you kidding?" and I said "No, I checked it on the web. We need to use something else or you could get pregnant." And she was upset but understanding.

She was upset that I didn't just KNOW that by having a headache and not wanting to see a movie TRANSLATED in woman-ese to "I'd rather just go have sex with you now." But still, why is she passing up the offer to do it Tuesday when the next time we can will be Sunday. (Prom friday, friday night she's changed her mind about staying at a hotel because she doesn't want to be a 'i got knocked up at prom' statistic when it was HER idea for a hotel! I'm staying at her folks so we can leave early Saturday morning for great america and won't get back till late so that leaves only Sunday available.

Why is she so wishy-washy with having sex now? (even with giving me bj's and acting like she does when I know she doesn't like doing it) I don't SEE or FEEL the signs that she's cheating on me (because I am scanning for both!) so what gives??