Kirsten, what you describe sounds so much like me in high school it is scary! All i can say is, it will get easier. Your future college schedule of class 15 hours a week will afford you much more flexibility, it will be easier to work around the illness. You just have to hang in there.
Also, as someone in her mid-20s I can tell you, there will be ups and downs, but overall life will improve dramatically when you leave your teens. Hang in there, and I am sending you all my sympathy. There isn't anything in the world that would make me go back to where you are now.