Since you say your dad is being very supportive with you, I think he would understand you dropping those classes. And you're not quitting, so don't feel like a failure. It would be different if you just quit going but you're not giving up. If it would be a great relief to you to drop then, do it. You're very young and will have plenty of time to go to school. Do you have a therapist that you can talk to? That might be a good idea, also. I can't help you on your dark feelings because I don't know what to say. Other than we're here for you if you need us.