Boyfriend Won't Let Me See Him Naked

Me and my boyfriend have been going out for six months and haven't had sex. Hw won't even let me see him naked. He's seen me naked because I sent him nudes. He doesn't ask I just get horny. I've never even seen him in shorts. He's spent the night and worn really baggy shirts and sweat pants to bed. I'm not trying to be a person who is only there for sex but sex is important. I ask him about it and he says he wants to have sex, it's just body issues. He recently started wearing jackets everywhere we go and sleeping in hoodies. Its like he's trying to hide from me. I was fine with wearing short sleeve shirts before and now he's completely trying to cover up from me. I dont understand why.