How do I get my dad to take my mental health seriously? ?

Have a session with the school counselor about this, and try to engage the counselor in your father's taking your plea for help seriously. It will probably involve them seeing the counselor to talk, but that's a good thing. If he still denies your need, and your mother can't do anything ,and you're stuck, call your local mental health center and talk to somebody there. It wouldn't hurt to try talking to the family doctor.