Help me with my insecurities and hurt heart please!

[60mm]

Hey ladies, I'm going to try and keep the backstory short and thanks in advance for any words of wisdom!

I started dating my girlfriend on new years 2009 and she's the first person I ever found out what it's like to really love and be loved by. By July we were living together and happy. We were both unemployed and were looking hard for jobs but it's not a great time to be job hunting as I'm sure you guys probably know. Anyhow, I was supporting both of us off of my savings and although it was stressful for us, we were doing good and were happy together. In December I finally got a job which was great news but it had a hefty commute (~2 hrs each way) and I started off working double 14-17 hour shifts because we were broke and I was trying to make sure we had rent/food/etc. December ended up being a distant month for us because I was often not there because of work, and when I was there I was simply beyond exhaustion. I would text and call her as much as possible and encouraged her to go out with friends and stuff to keep occupied until my schedule calmed down. Then on the 1st of january, our anniversary, she broke up with me. Totally devastated I moved out onto my own and found out soon after that she had cheated on me with a person I thought was a good friend of mine days before we broke up. I felt like such a sucker because I knew they hung out all the time and I encouraged it because I thought it'd be good for her to get out.
Fast forward to June. She had sent me a few emails through the last 6 months to explain how she cheated because she felt like she needed attention and fell for it when the guy told her how much he was into her and how badly she regretted it. She would email me about how she wishes we were together, etc. I knew I still loved her so I gathered up all my strength, tried to swallow my pain and started talking to her again. She told me she'd been seeing a couple guys casually but still loved me so we got back together. Here's where my problems and questions come in.
As hard as I'm trying I still feel so insecure and paranoid. I worry whether I'm as good as the guys she saw during our time apart, whether she's dating me out of guilt, is she going to cheat on me again, was I a fool to get back together with her again, etc. No matter how hard I try it won't go away and I've noticed her looking a bit stressed last night her so I asked her what was going on. She told me she hates how every time we see each other now, I always end up talking about "serious stuff". Which I guess I do, I've been talking about all my feelings and our relationship a lot because I still have a lot of pain and don't want to bury it. I want us to be open with each other. I want us to have a healthy relationship and I know be being so insecure can ruin it but I don't know what to do about it. I know dating someone who brings up hurtful subjects often surely isn't fun. I feel like if I keep talking about it with her I'll sabotage myself, I know women don't want to date a man who's so insecure. At the same time my pain is so real and I know it didn't happen because of my faults. I don't know, just confused, hurting, insecure and wishing I knew what to do!

[BEECATA]

She's a slut and a whore. If someone cheated on me I wouldn't be stuck on them. Have some pride man.

[Gigabitch]

If she really wanted to make this right, she wouldn't be trying to dismiss your concerns. She's the one who broke the thing, and instead of trying to fix it, she wants to sweep the pieces under the rug. This is a red flag. Recognize it.

[60mm]

@Gigabitch Well I should've mentioned that that was the only time she wasn't totally supportive for me while I talked about it and she was in a cranky mood after just getting home form a bad day from work. The next night I had some drinks and it got to me and she listened to me bawl and talk about it for nearly an hour and was super supportive. She's been super supportive everytime and I bring it up every time we see each other, the night. It upsets me but I feel like I have to give her some credit for being human and just having a bad day. Is there anything I could do/ask to see if this really is a red flag?

@Beecata Don't mean to be dismissive but I have plenty of guy friends for advice, that's why I put this in Ask a Female