PLEASE HELP! - thinking of breaking up with my girlfriend...?

You really sound like a very considerate and sensitive guy. If you stay with someone because you feel bad or sorry for them, that is a bad sign. Believe me, you are gonna be sad all your life as you're there not because of love. Plus, this girl sounds like a psycho. It's better to leave now than when it would be too late as you will definitely get used to her companionship and then it's gonna be hard for you to let go of her no matter how miserable you are with her. Good luck my friend.