I think you should follow Steve Wellams' advice very closely. Think about what he said about the higher rate of suicidal thinking when young people begin anti depressant treatment. I myself once experienced a period of constant suicidal thinking as soon as my medication was increased, it was unpleasant for both me and those around me. You don't want to be in that situation at all.
You want medication because you want to feel better. This is understandable. But you are not receiving adequate counseling. The lady you are seeing isn't equipped to deal with your issues and she is very probably under qualified to deal with anything other than people who feel a bit upset. Like Steve Wellam said, answers lie within therapy, and adequate counseling may really help you. Going down the medication route carries risks. If you go down the CAHMS route, you can get therapy from a qualified therapist.....so I think that is what you should do.
Your GP suggests it, I suggest it, and Steve Wellam has said that you need adequate counselling. If therapy reveals that your condition is serious enough to warrant medication at your age, then this should be done by a psychiatrist at the CAHMS and you will be closely monitored.
I agree that the confidentiallity is an issue to you and it is causing you concern. However, your health is at stake here, and that has paramount importance, so I think that you should go back to the CAHMS, tell the whole truth, and that way you will get better faster. It seems like if you don't do this things are just going to be dragged out for longer and longer.
Take care,
Steve