Here are some good things about college. One, if your IBS is flaring, you can chose not to go to class. Not really an option at the high school level, but in college you are in charge of yourself. So long as you take your tests and turn in your papers and read your materials, class is pretty optional (at least I found that it was--heck, I found reading was fairly optional, but then I'm an A-class BSer and could bluff my way through class and papers and even tests).
Secondly, there are a lot of clubs on college campuses. This makes it pretty easy to meet people and spend some time with them (that doesn't involve food), but not be committed to hanging out all of the time. I got involved in the anime club my senior year and had a good time for a few hours every Friday night. No major time commitment, but some fun anime and some social interaction. I also made heavy use of the online community for friends. Not the same as in-person friends, but better than no one at all to talk to. And, of course, it's easier to open up to a comuter screen than a real person, so if it helps you to get things off your chest about your illness, then it's a good thing.
Then, there was MY apartment. I went off campus with a friend my sophmore year. She left partway through that year and I had an apartment to myself the rest of the time. It can be kind of lonely, living by yourself, but the private bathroom is the way to go! If you go away from home to college, that might be something you want to look into. Colleges tend to discourage that, especially for freshmen, but heck, most of the time it's cheaper than room and board--especially if you can take a small apartment in someone's basement for a good rate. Then, when you're feeling well, you can invite friends over to your place to watch movies, play games and even have something approaching real food for a meal. It's always easier on the system to be in your own place when you're hanging out. And most campus-bound kids like to get out and go somewhere else for a while.