Just from my own personal experience, it's like what others have said: psych meds are a crapshoot. Some will work for you, some will do nothing, others will make you worse.
What works for one person will make another worse, and what makes one worse will work for another person. It seems so random, but hey, what'd ya expect with trying to do medicine for something as mysterious as the human brain?
Not necessarily. When I found a med that worked it took only about a week for it to kick in, despite the expectation of at least two weeks.