Of course it's possible that you simply weren't compatible with your ex-girlfriend.
However, you might wish to address
why such was the case. Also, depending on how long you've been away from the dating scene, you might wish to think long and hard about why you don't seem to be compatible with many women. Of course, it could just be that you need some time to recover from your previous relationship. Don't rush it.
(Incidentally, get over the homophobia thing, too. Yes, it's there--otherwise you wouldn't have made such a point about mentioning that you were not gay. Besides, a lot of gay guys know a lot of nice straight women!

)