Sex Drive

So my boyfriend (he is my first/only boyfriend) and I have been dating for a year now, and I am super in love with him. For a while I had a very high sex drive, and I loved doing things because it made me feel closer to him. In the last two months my sex drive has basically disappeared and I have no idea what happened. He thinks he did something wrong, and I feel so bad because I don’t what him to think it’s his fault! I just don’t want to anymore, and I’m not sure why. He always asks for consent before we start, and he’s doing everything right, I don’t know what’s wrong with me. What causes a decrease in sex drive in young people?? (I’m 18, shouldn’t I be at my prime!)