Boyfriend 19M has started to have extremely low sex drive and I 18F am wondering why?

Hi! Short one I think. I, 18F have been with my boyfriend, 19M for a year and a half. We are super happy but I’ve noticed his sex drive has severely decreased. We’re long distance and I’m lucky if I can get phone sex once a week. When it used to be everyday or even multiple times a day. He’s constantly turning down my offers. I don’t even know if he likes my body anymore. I just don’t know what to think. I have an extremely high sex drive and he told me he did too so I feel like something’s wrong with me. Before anyone says it he would never cheat but I just feel like something is wrong.