Why do guys like to play with my emotions?

I have been with this guy for 2 years and we have been living with each other for that long also. He is the best guy I've had so far but he has a downside. At first we were in love like crazy even tried to have a baby the first few months but then each little petty fight would become something unnecessary. He is bipolar and says hes not committed to me but he loves me. I know he is not ready to settle and I am. He is my dream dude but I am in love and so blind to the wrong that I can't escape.