I would advise seeing a psych and getting an SSRI if you can... plus eating healthy, getting exercise regularly and having a regular sleep schedule can really help.

I know how you feel as far as feeling weak and useless... if you do have major depression and not dysthymia then medication will certainly be necessary, but the eating/sleeping/exercise will help a lot as well regardless of whether you're on meds or have access to them or whatever. Exercising regularly has been proven through multiple studies to be as effective as a standard dose of an SSRI.

Good luck and take care - I know how you feel but you can get yourself out of it!!