My sex drive is GONE!

Shabana
I've been dating my bf for about two and a half years now. We've always had amazing sex, but for some reason lately I've had no desire to do anything sexual with him. Like if we're in bed and he starts feeling me up I tell him to stop, complain that I'm tired, and just get super annoyed. 
I take Vyvanse every day and I'm not sure if this is causing my decreased sex drive and moodiness, but I'm scared this is going to ruin my relationship!
It's weird because I get super horny when I'm by myself and I wish that he's there at those times, but even when I'm horny and he comes over I instantly get so lazy and don't feel like putting in any effort to have sex.
Has this happened to anyone else?!? Any tips on how to get myself out of this rut?!