It might take longer than that, I think it was about 2 1/2 to 3 weeks before I noticed anything, and then it was not a slap you in the face type thing, more of a you know come to think of it type thing.
It's also possible it's not a high enough dose - I know I started with 15mg 2 a day, now I am up to 30mg 3 times a day.