If you're living with your parents, work up the courage to tell them to begin drug testing you each week on a random day, and to not stop until you're out of college. Also, it's obvious, but you need to break ties with everyone you're friends with who do drugs. Try spending more time with the friends who do not do drugs. Take up a hobby, or get a job (or volunteer), so you have no free time to do drugs. Do not allow yourself access to any medications that you could take.

Begin writing a journal when you're feeling emotional/depressed. Post on 4-ch for advice if you feel overwhelmed.

Good luck, OP.