Sex&realtionships

I’ve been with my partner for 15 months .My boyfriend has a very very high sex drive and wants it mainly everyday . I don’t really enjoy sex that much so it frustrates me when he constantly asks but I feel so negative not giving him it and I’m always thinking he’s going to find it from someone else . Is it my fault if he does it ?

(I’m 19 ) by the way

Anyone got any advice for me ???? X