mth, i agree with the others, that it sounds just like a real deep depression. If i where you i would most defenitly see a doctor. Deep depression is not just mental illness, but meanly physical. It's a biolaire disfunction of the brain. (the neurons in your brain don't function the way they suppose to) For years men thought that a shrink could do the trick, but since quite some years now, people acknowlegde it to be a real illness.
The doctor will subscribe some medicen, and give you a few guidelines for your live. And yes, as a support (cause it will help) he will advice you to see a shrink.
To put it down to you the hard way: many people try to beat it on their own. Don't let the successtory's fool you, those people didn't have a deep depression but where just depressed (which can be bad, I agree, but is purely mental).
With deep depression the shit is that you can't just 'beat it' yourself. You will need help. At first it might look you're doing better, but if it really is a deep depression, you will slide back whitin 6 months. It's a common thing with deep depression to have periods that things look better.
Do yourself a great favor, go see a doctor and don't let yourself get send away with a: 'id'll all be ok, just take a rest" cause that's worthless. Insist on good help and diagnose!
Best of luck to you!
:boxer: