I feel super super frustrated because of my teacher’s attitude to me. What should I do?

I don’t want to get into a lower level of history class. I can keep a high ranking in history tests all the time! Sorry for my illogical sentences!
There’s that. I got into a serious mental depression condition during the summer vacation, so I didn’t finish my history assignments. I was not capable to finish all parts of them. Yes, exactly, my history teacher was annoyed by my bad behaviors. She decided to kick me out of her class which offers a better learning environment for some students who can do a good job in test. She said my behaviors showed my negative attitudes. Well, how can I explain to her? Tell her how a bad mental illness i have? Or just act like a dumb person? As it turned out, I chose the last option. I tried to explain ambiguously because I really didn’t want her to know how weak I am. By the way, I have to claim that mental disease doesn’t mean weakness, I just thought she would regard me as a weak person. Afterwards, she requested me to finish those assignments, or I would be kicked out. Current tasks sucked me either. Then, I didn’t finish her assignments until the deadline(yesterday). But I asked for sick leave yesterday because i was so afraid to be kicked out. I just avoided to meet her temporarily. Today, I still can’t get to school with enough bravery. What should I do?