cheating in his dreams?

so he called me over to "cuddle" well why we were all cuddled up he was in a deep sleep and he was literally thrusting in his sleep and was hard as hell.. and he had pre-cum trough his pants. when i told him it was wet in that area he said "probably because of the dream i was having" and i feel like he was dreaming about another girl that he probably knows or his ex that he's still hooked on. i don't know why but it pisses me off and bothers me. we had sex after but like i feel like he wishes i was the probably hotter girl in his dream.