Depression sucks ass. Good posts in here. Exercise helps me a lot.
I take St. John's wort as well, it seems to stop the fretting a bit. But jogging definitely is the key for me. I'm feeling alright now, but I haven't been making any music for about 6 months. Everything feels formulaic and soulless - maybe I need to learn an instrument or pick up another hobby for some inspiration.
The worst thing about this shit is losing almost all motivation to do stuff, vicious cycle etc. And the fact that I'm on edge a lot of the time, acting like a bitch, not being sympathetic, not able to concentrate, not enjoying stuff. I just don't feel like myself, sort of like the stuff Franklin was talking about, even though I think my depression is not that severe. I feel like I can do twice as well as this. The motivation is probably the last thing that comes back, I'm not sad anymore, but still not really motivated - don't really give a shit about my exams either.
Just don't give up, and remember it will go away eventually. Do stuff, even when it's hard to get off your ass and you don't see the point. Talk to people you love, talk with friends who understand (I have friends that are suffering from it as well, and it helps a lot talking with them, people that don't know how it feels can get you on edge even when they mean well). Perhaps you will get pissed at people saying you need to get off your ass, but you will see that it helps. If they ask you to come over or have a laugh: go! don't stay at home alone. Go outside.
All the best.