Oh my goodness, I know exactly how you feel! I had to miss a lot of school because I had a mental breakdown and had to go to the psych hospital...for the fourth time. It's funny, I left because I was overwhelmed, but when I came back, I was so overwhelmed with make up work and everything that I was throwing up during class from all the stress and anxiety.
What I found that I had to do is cut back on about 3/4 of my activities. And I even had to quit my job that I loved so much. But I have a lot more energy. Is there anything you can cut back on?
Never forget that you are more important than your education, my dear.