Stress!

I'm a senior in high school that is a Gifted and Talented student (IQ is much higher than average on a specific subject, mine is reading/English) and in multiple advanced courses. I also happen to struggle with depression and anxiety. I am on medication, and seeing a therapist. I stay on a schedule, a written schedule, that my therapist and I plan out, and yet I still cannot keep up with the classwork. I find myself falling asleep at any moment I relax a little too much, I'm constantly sore, and my period is late by two weeks. I have massive chest pain, like a vice holding my lungs in place, and I feel like I am going to break at any second. I haven't slept in three days, and I'm scared I'm getting bad again. Can anyone please help? I'm trying To get caught up, but I simply cannot find the motivation to keep going with everyday tasks, let alone homework that won't apply to my future.