Boyfriend doesn’t want to have sex??

Okay, so let me start this off saying: no, I don’t think he is cheating on me. He works the same hours I do and we live together and are around each other a lot. But anyways, I am so confused. My boyfriend and I used to have an amazing sex life. Like every chance we got, we did it. About 5 months ago I got a new job and i was tired a lot and on the weekends we were busy but I’m still wanting to have sex. I miss the physical connection of it. Is there something wrong with me??? He says it’s not me but I don’t know what to do to help??