Antidepress not helping with fatigue but a recent prescription for a pain killer did. What's up?

I have been taking antidepressents for about two years and have tried a few different ones.  None seem to help with the fatique or my problems focusing.  I recently had some teeth removed the doctor gave me a prescription for pain.  I could focus and had more engery that I have ever had on antidepressions.  I don't feel like I am really ever been in a depress state just stressed alot.  So what's up why do I feel better with something for pain, that any of the antidepressent that I've taken?

[Sunnylife]

I guess it helps when our feeling & emotions are numbed.