So sorry to hear that you've been plagued with all these health problems. I am a college student too, and know that having IBS alone doesn't mix with school work - let alone all of what you have.
Definitely check out Heather's books. Then start on the basic Breaking the Cycle diet she recommends to get your body stable. Then slowly start increasing some safe foods into your diet.
There are a lot of people on here trying to gain weight and have done so by eating lots of safe breads that are high in calories.