Re: I think my girlfriend is cheating on me
WTF?! Do what is the hardest in your mind, that is talk about everything that is bothering you and what you feel. If she is not understanding, give her some time then ask again. If you can't communicate with her, then the relationship will not work. A general mix of things that make relationships work is trust, mutual respect, communication, and love. If any one is missing, including sex, then it falls apart eventually.
One thing to remember, as a male, you'll enjoy many, many more relationships as long as you're more mature and can handle it. Don't get hung up over one girl, there are many, many out there. I'm not saying don't love, I'm saying don't feel like you're obligated to go through emotional hell with her. That's why I encourage open communication, do not let her close it. If she can't communicate, even if you give her time, you have to be man enough to figure out that it's not going to work. By the way, "love" changes over time. What you feel now does not necessarily mean that you'll feel it a year from now. Put your emotions aside and figure this out logically for a moment and decide if it's a ride worth taking. Ultimately, you're in control and have to put on the big boy pants and man up to a potential baby. ASK for a genetic test to make sure that it's yours. Many people cheat, not all, probably 1/2, so make sure to be careful, honest, and direct. If she throws any tantrum, call her out on what she is - a whiner and you won't tolerate it. Change the words to your own style, but be firm and always voice your stance - politely when possible.
But, based on what little you wrote and gut instinct, I say it's time to take a dump.