When I was starting Grad School I felt bad when I'd go out to bars and my boyfriend (still in undergrad, 2 hours away) wasn't there. I got over it quickly, and although that relationship ended I still had a fabulous time during my first year.
Now I live with my boyfriend and believe me I feel ABSOLUTELY NO GUILT about going to parties/bars/clubs without him - love him to pieces but social environments without him there are super fun, too!
You don't have to go to EVERY party - I know you feel like it's disrespectful but unless "frat party" stands for orgy on your campus, if you go with your sisters/friends who are respectful that you have a boyfriend you might end up having a good time.
"Every so often" rather than "every night" is what keeps it (at least, in my opinion) on the respectful side.
Clubs are a little bit of a different environment, what with the dancing (and I'm guessing you're under 21 since you didn't mention bars) and lack of much else to do.
Initiating events and fun things to do yourself is a good idea. Also, if you go to the gym on campus, ask a sister to come with you. Yoga classes with a friend are also very fun.