decisions, decisions... :-/

[tballs]

I sort of have a dilemma. Today a guy asked me to the Delta Sig semi-formal, which is cool because we know each other okay and I think he knows I have a boyfriend and everything, but Pat was supposed to come visit me after he got off of work and we were going to hang. I told the guy that I would go, but Pat said that he would still come down on Friday if I am out of there by 11 or so. I don't know how to tell Delta Sig boy that I want to leave early to see my boyfriend... And also, Pat and I made an agreement that I wouldn't dance with any more boys (in a grinding sort of way) because it's disrespectful to him. How do you go about not dancing w/ boys at a dance if they come up behind you and stick their weiner up your butt? Do you let them down gently and say "sorry, can't, I have an overprotective boyfriend (j/k)", or do you say something like "get your dick outta my ass you a-hole", or I could lie and tell him I have some sort of fungus growing down there. Any suggestions? It is now open for discussion.
Questions to consider:
Is there a nice way to let a guy know you have a boyfriend while trying not to hurt their feelings?
Should I even go to the formal?
Am I the whipped one in the relationship?