I just wanted to let you know that I understand how you feel. Here's a few tips I have. Be honest with your doc about how you are feeling on the medication. It took a long time for my doctor to get me on the right meds (especially when I was that age), part of it was because I wasn't honest with them, even on the wrong meds I felt a little better than I was before but the problem was when the depression hit it would drop me lower than ever, but because I was having more times where I felt I was doing 'okay' I didn't let them know.
Second tip, when you are being honest with your T let them know that the idea of suicide is there but you have no intention of going through with it because of the pain it would inflict on others. It just concerns you that those thoughts and feelings arn't going away.
Third tip, do a few family therapy sessions, I know it is scary and everything in you is screaming 'NO', but it will be okay. It took me a long time till I was willing to do that and it really helped because the therapist was able to keep my parents in check, and when they were getting out of line with their way of thinking she would back me up. Her main goal is to be there for you, not for them.
I know it feels like you can't handle this sometimes, but I know you will be able to get through this. Try finding a purpose for your life; it will help you feel better when you are able to help others. No matter how low you've sunk there will always be someone out there who could use someone like you.