Not interested

I’ve been with my boyfriend for over two months now and lately We haven’t been having sex like usually it’s been over 3 weeks since yesterday we did it but I definitely could tell something was different he wasn’t as hard as he usually is and the way he acted was weird. I’m just not sure what to think, is he cheating or is he just not attracted to me during sex. Anymore. I have been on a new birth control and it has changed my appetite for sex, I’m not as wet as usual and I have no sex drive.. please comment below thanks