Topamax does
not get rid of migraines. It
lessens the frequencies of them.
Not everyone suffers from the side effects of Topamax nor from
all of the side effects. Therefore, you may not be one of the ones that loses weight. Matter of fact, you just may gain weight.
If you are not seeing any benefits (your migraines have gotten worse and/or increased) then I strongly suggest that you inform your treating physician. Maybe Topamax is not for you.