Feeling confused

I’ve been with my boyfriend for 3 and a half months... I love him very much but he just doesn’t turn me on. He wants to have sex and he’s begged and pleaded for so long but I just do not feel the sexual spark I want to feel. (He’s my first boyfriend and I’m his first girlfriend) He’s so much more into this relationship than I am and I feel so guilty. He says “you’re the only one I want” but he’s not the only one that I want. I’m getting frustrated with the constraints of being in a relationship but I still love him... I just don’t know if I can stay in a relationship. Has anyone ever been in this situation before??