Stress ruining health ?

Since starting school this semester, my health has been exponentially declining due to the ridiculous amounts of stress I have been experiencing. I'm taking all AP classes but it seems like while other people who take the same level and even higher level classes than me have less stress! They spend only a few hours on homework a night while i get an average of 3-4 hours of sleep a night and sometimes have to pull all nighters. Its just so frustrating because I believe this stress is the cause of my
1) recent dramatic hair loss (i can nearly literally count the hairs on my head now whereas before the start of school, i used to have very thick hair i could barely put my hand around)
2) constipation and excessive bloating- i have a natural bowel movement about once a week, and even so i frequently have to use laxatives. It gives me constant stomach bloating and discomfort.
3) fat gain, especially around the stomach, despite the fact that this year i have started to get in at least 30 minutes of excercise a day. The fat is not going away; rather it seems like it is getting worse with the excercise!
4) flatter head- this sounds strange but i have always had a flat head shape in the back of my head, and it seems like it is getting flatter and flatter and more towards 90 degrees flat, making the rest of my body seem awkward and huge. It makes me very self concious!

Is there any way I can cut back on stress while maintaining all my classes? Is there a way to help my health problems? Also is it worth it to be spending all that time on excercise when it doesnt seem to be helping at all?