Did he cheat?

Last night my boyfriend was out late, and I fell asleep before he came home. It must have been 2 when he did get into bed with me. This morning when we woke up he wanted to have sex, and we started fooling around. I went down on him and his dick smelled and tasted funny. When he came his cum smelled and tasted nasty, rank. So off that I gagged and couldn't swallow it. Just the taste and smell of it in my mouth and on my tongue made me sick. Do you think he was with another girl?