Guy is cheating on his girlfriend.with me.again

So I'm a sophmore girl, this guy is a senior. He has a sophmore girlfriend and they've been together for about 2 yrs with a few break ups. About 2 months ago he started texting me cause they split for a lil bit, then they got back together but he still texted me. He flirted a ton, even talked about "going to yellowstone's guysers and skinny dipping and then we could fall asleep under the stars in my truck. Maybe a lil naughty things will happen. " --summary of some of the stuff he'd tell me. He'd also call me gorgeous all the time and wanted pics and stuff. I told him wait aren't you still with her? He said 'yea I know I'm being bad. But I just want to get to know you better'. I told him that I wanted to get to know him better too but that I didn't want to hurt his girlfriend and I didn't want to be the one to ruin there relationship. He assured me everything was fine.

Then his girlfriend keeps seeing him txt me all the time and flips, I tell him I knew that was all a bad idea and that we couldn't be friends cause that's what it was gonna take. He apoligized and felt awful. We stopped talking. Things started going great for her and him. They were closer then ever.

Now recently, he's been texting me again. We were snap chatting yesterday (app on ipod/iphone where you take pics and send em with a caption) and mine were all normal but he was sending pics of himself and his abs and shirt off and everything asking to see "more" of me and everything. I didn't of course, but he wanted me to take more revealing pics and send em and he kept saying he'd give me anything I wanted and stuff. I don't know what to do. Telling him to stop doesn't work too well cause I've already tried.

I don't want to hurt his girlfriend or split them up cause they are great together. But because of the first time he pulled all this on me, of course his girlfriend hates me. But she got her older brother who's a senior to, too. We were great friends. Also they've spread crap rumors about me. I don't want it all again:/

He is cheating with his Girlfriend
He wants dirty stuff with you
he will not definitely accept you as his Girlfriend at any point of time
be away form him