Sounds like your stressed and being stressed isn't good for anyone. If you feel that you can't take the course anymore maybe you can talk to your school and ask them what some other options are. If they insist on you taking the course stay in till the end of the year or you can ask if there's a diffrent way you can earn that credit. Some schools offer sign language as credit. If you feel as your metal health is declining I would definitely talk to your school and see what other options you have.