Why won't he sleep with me?

he has told me he thinks I'm really hot, I can definitely feel the sexual tension between us yet when I asked him to spend the night he refused. Next day he kept talking about other girls and mentioning that we were friends... that he would not be a home wrecker (I'm separated, but not divorced), yet he goes and sleeps with another separated chick. am I that ugly that he won't sleep with me even when he sleeps with anything that moves?!