Sex----?

My boyfriend and I lately have only been having sex like once a month twice at the most, usually it's once or twice a week.. Idk what's going on.. I know 100% he's not cheating or even talking to any other person, our three year anniversary is coming up next week!! I think it's where he works such long hours and being outside all day and working 7 days a week on top of that, for the past 3 weeks.