How long does it take for Pristiq to work for depression?

I started pristiq generic 50 mgs 2 days ago. So far I can feel better gastric motility and slightly more strength especially upon initiation of a movement.

I'm in month 4 now. No change. Should I stop?

Hi, marilia! You have to be very patient with psychiatric drugs because they just don't work instantly like aspirin does. Many people report some improvement in about 2 weeks, but it can take 4-6 weeks to feel the full effects and 6-8 weeks for the drug to reach steady state therapeutic levels in your bloodstream.
As Sidekick says, sweating is a common side effect of Pristiq so we know it's starting to take effect. You're lucky that you're not having other side effects too, although the majority of people don't.
Give it some time, and if you're not starting to feel better in a couple of weeks let your doctor know but I think you'll do fine.

Well, we know it’s in you if you’re sweating! Lol. It can take some time, so be patient. General rule is to look for benefits around the two week mark, and expect a full response around the 4 week mark. If at week 3 nothing has changed at all, give your doc a call. It’s way to soon for you to just quit it though.