I'm wondering if your depression may be due to your subconscious worry about your future, since you said you are not planning on going to college or getting a job. What if you thought a little bit about what kind of work might intrest you, to see if you could find something that would inspire you to keep moving. Your decent grades means there will be a lot of opportunities for you. Having a future goal can really lift one's spirits.

Also, the oxy is a problem. If you are still using drugs, they can definitely cause depression. In fact, drug withdrawal is used as an animal model of depresion lab experiments. You pay for the high with a reduced ability to experience pleasure afterwards. If you can't get of the drugs by yourself, definitely seek help for that - it will be worth it.