I seem to have problems with women I go after?

Before I started dating the girl I'm with I used to hit on everything and anything I thought was hot. Then one day I decided to go after the girl that I had hung out with a couple of times and had not really thought about. She's pretty and has allot of really good qualities. The sex for her is good she orgasms all the time and I have not had one orgasm. I have been told that I should not break up with her over sex but I'm still on the fence.