Sorry to hear you're going through a difficult time, PR.
For what it's worth, based on personal experience I think Torie's right, as he tends to be - it's certainly not a cure-all, and not replacement for medical help if needed, but excercise can do wonders for your mental state IMO. Your mind and body are the same thing, after all, and depression's a physical condition.
That said, do get it checked out - if necessary there's an anti-depressant out there that suits your chemistry, and a doctor who can find it. Best wishes.
