Hi Lucie,
I completely completely understand how you are feeling. I am currently a 23 year old college student in California and I have lost of first hand experience dealing with the college system. As the previous post mensions and I can not stress enough GO GO GO GO TO THE DISABILITY SERVICES DEPARTMENT AT YOUR SCHOOL!!!! It is specifically designed to help successfully get through your classes and deal with your disability. The most important thing you can do through disabilitly services is have them write letters to your teachers and tutors explaining your situation this includes any accomidations you may need.
I for example have on my accomidation letters explain my health situation (having CF and CFRD) I have a clause excussing any future absences because 10 times out of 10 I am missing class because I am either at the doctor or I am sick. My letters also include my ability to negociate due dates for large projects and test, permission to eat, drink, and have my cell phone on in class (in case my doctors need to get a hold of me) and allows me time and a half on tests. These letters are very important in explaining to your professors about your current health situation.
Don't think of it as taking advantage of the system or using your disability to get ahead (I know alot of people feel guilty some times for asking for "special" treatment) DON'T!! The fact of the matter is we live very different lives then the average college student, we can't spend 6 hours a day studying because we have to work just as hard at keeping ourselves alive as we do on getting good grades.
My other recommendation would be to go to your teachers/tutors office hours and have a one on one conversation with them, not just sort of a casual mensioning of it. Look them in the eye and say this is my circumstance, this is what I have to do to deal with it and stay in school, how can we work together to make my college life/situation more successful. I have found that when you are open and honest with your teachers then they greatly respect the effort that you are putting in. If they don't respond well to this approach, this is also where disability services and those letters to the teachers come in handy because they can be your advocates when you just don't have the time or energy to be one for yourself.
Any further questions about disability services, please feel free to ask, after 5 years of college I've kind of become an unofficial pro. Good luck,
-Annie