Unusual behavior from girlfriend -- opinions needed

Hey, guys. I've been with this girl for about two years and we've been living together for half that time. Some behaviors and signs have come up that make me think she might be cheating, and I'm wondering what you guys think.

What first got me suspicious was the sudden appearance of bruises on her upper thighs -- small, finger-sized bruises -- some of them in a row like a hand grabbed her. These are in places where I don't grab her when we have sex. When asked about them, she would either make up an excuse, like bumping into things, or claim no knowledge of how they got there. She says that she bruises easily, but this is a sudden change and I never saw these kinds of bruises before. I caught her trying to hide a new bruise on her ass, and she said I did it when we had sex, but it wasn't in a place that I even touch her.

Around the time these bruises started appearing, she suddenly began buying sexy underwear and lingerie (no interest in this before), getting in shape, dressing more nicely, and tending to her appearance better.

She started doing different things in bed out of the blue, but normally she was extremely reluctant to be adventurous or experimental. Her sex drive seemed to increase as well, and she wanted more sex more frequently.

She started biking to work, showering there, and working more overtime than usual.

At first, I asked pretty docile questions about the change in behavior, and she was extremely defensive about it. As the behavior continued, I came right out and asked if she was seeing someone else, and she swore that she wasn't and would never do that.

Her co-workers are really weird around me: they keep very grave expressions, body language, and tones of voice, and they don't respond to good-natured conversation. They find excuses to avoid me in social situations.

Am I being paranoid, or do I have reason to be suspicious of her cheating? If so, how to I root this out and get it into the open?

hmmmm,.............i dont know she and her co workers sounds to me like mesyy sluts.

or maybe they think u abuse her. or they help her hide that she is cheating.
or in the ****ed up world of today maybe she is doing bondage sex for money and wont tell u.
or she have a pimp.

but i think u can only ask her or waste time follow her once or ask her co workers whats going on that they act that way towards you.

but i think best way is to tell her she tells u or its over right now.
dont waste your time and heart on trash . she open her legs for u so she have a certain trust and can also be honest with u.

I agree with Fruitss.

It sounds like she is cheating with someone she works with. And from the description of the bruises, he is probably better in bed than you.

Yes it does sound like she is cheating. She would never admit to it, so it's useless trying to talk to her about it. Cheaters usually would get all defensive and mad when questioned. With her adventurous new side of sex, she is probably using you to practice on so she can be amazing for her new bf.

You should get out while you are still in control rather than when your hand is forced. Do you want to find out if she is cheating? I think I would rather not take the risk and get hurt and try and move on.

Start detaching yourself emotionally from her. Treat her as a sex object(sounds like what she wants anyway) and nothing more. Be cordial, but stop going out of your way for her. Start looking for other girls. Start treating the relationship as over, and just get what you can out of it. Find another girl then break up with your g/f kick her out or leave(it will hurt more if you leave her for another girl).

Agree with BackUp, it's harsh but I have a very strong feeling she is cheating on you. There's just no other explanation besides her being abused at home, which I highly doubt. Good luck mate.