Coping with depression.

I went to the doctor today for my first evaluation in over 8 years, and my doctor/therapist asked me questions and soon came to the conclusion that I may be despressed. I had a traumatic loss of someone extremely close and dear to my heart exactly a year ago from the 12th of this month. Ever since then I've been extremely angry, unmotivated, resentful, and all I ever want to do is cry and lay in my bed. My own boyfriend of 1 year and 4 months had had trouble getting me to open up to him, and when I do and he tries I help I just shut him out and get irritated. So obviously I also came to the conclusion that I am depressed, but I didn't think it was a big deal so I went along with my everyday life. Laying in bed, crying, hating the world, and not wanting to be alive (not in a suicidal way at all, I don't want to end my life, I just don't want to exist at all if that makes sense.) but so today she said with all of my symptoms; extreme irritability, lack of motivation and energy, constantly sad/angry/crying for practically no reason, and having episodes or anxiety/panic attacks, that she wants to start me on Zoloft, since I am only 15, she wants to start me on a very low dose and then I go back in to her office in two weeks to see how I've been doing. She also recommended exercise and being more active, but I already don't have the energy to even get up out of bed to eat dinner or go to the restroom. Anyway the point of all this was to ask for advice from anyone who is experiencing depression or anxiety like me and how you've learabed to cope with it, because mine is progressively getting worse, and I'm starting to get scared of being alone because I think horrible, evil things and I'm scared of my own mind.