Constantly wanting nudes

Alright ladies I need help! I've been a thing with this guy for about 9 months now and I've kept trying to ask him if he wants to you know become official. But he keeps shutting me down or changing the subject. He'll only text me at a certain time every night and I'll try to have a conversation but he only wants nudes. I don't know what to do! Do I tell him that I'm sick and tired of it, I'm getting bored and I don't want something just based on that. He's done it to me multiple times but I don't know what I see in him and why I keep going back. Please help a girl outtt😩😩