Don't want sex anymore?

I've been with my boyfriend for a year now and the past few months our sex life has been deteriorating. I don't want to have sex anymore, I'm not interested at all. We sometimes do oral but that's it. I've started to feel uncomfortable with him touching me and kissing me all over my body, I don't know what is going on. I get horny but I don't even like watching porn or touching myself anymore.

I'm terribly in love with my boyfriend, our relationship is great.

He's stopped looking after himself like he used to, he doesn't get his haircut very often so he looks less attractive, an I not sexually attracted to him anymore? I really want to get back on track and don't want it to ruin my relationship.

Thanks