My relationship is on the rocks, PLEASE HELP!?

[lovelost.]

I'm 20 in college, I have been with my boyfriend for over a year now. I love him deeply. College just resumed about a week ago, and all of a sudden I find myself being very upset and irritated with him. HE threw a couple of welcome back parties. I don't really like when my boyfriend dances with other girls. Dancing in our generation =grinding, popping, dancing extremely vulgar. Its just uncomfortable for me watching him do that with other females, but he wants to still do it because he says its all a part of having fun and he doesn't want to look back on his college years and think that he didn't have fun because of restraints being put on him. Anyways, he was getting a lapdance from a girl at the first party. That's when I flipped and left the party. We had a huge fight. The next night, he was dancing with some girls and I left the party again. We talked about it, but we didn;t really come to a soultion because he still wants to dance with other girls. He doesn't even have any issues with me "grinding/dancing" with another guy, it doesn't make him upset at all. To him, it's "just dancing" and we both know we're together so it doesn't matter. But I still hate seeing him grind on girls, get lapdances etc.
Thats ONE thing that has turned me off from him.
The second thing is, there is a girl who is known to flirt with other guys' boyfriends and make subtle passes at them. We both are kind of friends with her. But he goes out his way to text him and to pay her visits on occasion. I don't understand why? Especially when I confronted him about his flirting with her about a year ago.
The third thing is that, recently on his twitter, he tweeted one of his ex girlfriend to call and text him asap. I look in his phone and he has deleted most of the messages he has sent her. It makes me think he is hiding something. (and yes I know I am wrong for being in his phone)
all of this stuff has happened in the first week of school, it's just way too much and i find myself always angry with him and I don't want to see him,
what should I do?
I don't even know how to confront him or the situation