He's Distant

My bf has been distant sexually lately. Over the past 3-4 months he just hasn't been in the mood. I think we've had sex 3x in 3 months.
I know he was really stressed and exhausted during the holidays because he was working a lot of OT (10 hr days). 
I know he's not cheating. But I just feel rejected. We've been together for 2.5 yrs. 
I've tried to bring it up but I'm just not sure what to say. 😔