I haven't been on many for very long, but I've eaten quite few different happy pills in my day. Fortunately, I no longer need antidepressants. Whether they're an instant panacea or not depends on whether you have a chemical imbalance or, as you described, a type of soul cancer / circumstantial issue. Anyway, here's what I can tell you about the medicines I've taken that i'm most familiar with:
Buproprion (wellbutrin, NDRI) - This one I feel usually in days or hours. It generally felt to me like a gentle lifting of the "mood floor" compared to being off of it; I wouldn't dip quite so low on the mood scale. My brain adjusted to this one in a matter of months, though, and I was back to feeling pretty crappy due to certain life circumstances that didn't change while I was on it. This is probably the best one I've been on.
Venlafaxine (efexor, SNRI) - This one felt very unpleasant. Again, this one I felt in a matter of hours. I was very positive and high energy on this, but it felt like I had a rocket up my ass. I had *too much* focus, if that makes sense. This one also had an unfortunate sexual side effect for me. Depending on how bad your depression is, it may be worth trying out still.
Fluoxetine (prozac, SSRI) - I was on this one for years in high school. I don't recall necessarily feeling a change, but maybe because it was really long ago.
Again, I have no clue how any of these would play with your brain chemistry, but if you sought help and received any prescription medicines, my advice would be, if you find one that makes you feel more functional, to figure out what's causing the anguish and try to reorganize your life around what's important to you and remove those anguish-causing agents, to the best of your ability. Your brain and body will adjust to the chemicals, so, as Muz said, use them to get out of the pit before they wear off. Best of luck to ye, Magmacube_tr!