Im not attracted to my boyfriend anymore!

I'm not attracted to him anymore but he is the sweetest man ever. I get a lot of support and love from him which I'm so so grateful for but there is no sex and if there is, I really don't like it. I'm only 18 and want to have a fun sex life but I feel like we're an old married couple. I just avoid sex now, it makes me really upset and stuck. I don't feel the love for him also. It's mostly one sided, I don't know what to do..