How do I tell my boyfriend I’m not attracted to him anymore ?

I’ve been with my boyfriend going on 4 years now and I’m just not attracted to him anymore.. reason being I feel like he doesn’t care about his appearance anymore. He hasn’t had a haircut in months, his fingernails are always dirty, and his breath always stinks. I’ve tried to tell him multiple times in many different ways and he’ll change it for like a week and will go back to how he was. He’s not taking my advice and I don’t know what to do anymore.. we haven’t had sex in weeks and every time he tries to kiss me I turn my head because of it, he’s even starting to think it’s because I’m cheating. I love him and I don’t wanna break up, but I can’t deal with it anymore