Course Mastery

I had 31% course mastery in my Calc AB class. I log in a while later to find my course mastery dropped all the way to 8%. I have an assignment due in a few days, and I have to be at 40% for my class. I told my teacher about it, and she said she has no control over it. No new content has been added, and I have not been getting questions wrong (definitely not to the point of such a dramatic drop). What is going on? This is a terrible bug, please help.