arjck,
If you were my daughter, I would take you to a doctor or to the emergency room, I would give you a big hug and tell you that I would stand with you no matter what. I would not yell or get mad; I would get you the help that you need.
Unfortunately at age 16 you can't sign yourself into a treatment facility; it is something your parents have to do on your behalf.
One way or another, your parents are going to find out. It will either be because you tell them or because you go into some sort of medical crisis (i.e., withdrawal or overdose) where the decision is taken from you. No matter how difficult or distant your parents, I would hate for your parents to find out by an overdose or by withdrawal.
What is the worst thing that could happen if your parents find out? That they become angry? That they yell at you? That your mother becomes depressed?
So what if they become angry and yell -- under the anger is fear. And they can't be angry or yell forever. Your mother is responsible for her own feelings and responses -- including her depression. You aren't responsible for her. She, on the other had, is responsible for you as a minor.
The point is that after they finish yelling they will most likely take you to see a doctor and/or arrange for you to get help at a treatment/detox facility. And that is exactly what you need. Unfortunately you are in a situation that you are not going to be able to get out of on your own. You need professional and medical assistance.
What is the worst thing that could happen if you don't tell them? You could overdose and die. Let's see -- yell, mad, depressed vs. dying -- the choice should be clear.
The members of Sober Recovery can give you advice, share our experiences, and support you in your recovery. But we can't take that first step for you. You have to do this yourself. You have your whole life ahead of you. Please don't give up. You are worth taking that first step for.
SusanLauren