I am so, so sorry. I know what it's like, I was on Topamax for over 2 years. It nearly ruined my academic career, I went from a gifted student to failing out of college. I actually had bouts of amnesia and there are portions of my memory from those years that are just missing.
I didn't feel like I had fully regained my memory until about 3 years after I stopped taking it, and there have been times when I felt like my brain was relapsing. The only probable reason why I was able to regain my memory is because I stopped taking it at 19. Young brains recover more easily. Topamax works by lessening the synapses in your brain. I don't know why on earth anyone ever thought that could be a good thing. Synapses are what allow you to think.
After stopping it, I started doing mental exercises that are often recommended for older people. Playing word games, solving brainteasers, building puzzles, anything that stimulates your brain will help. The memory game is also good (it's normally played by children, the one where you flip over all the cards and try to match up pairs).
If you look up 'memory loss and Topamax' you'll be shocked at what you find.
It seriously disturbs me that Topamax is prescribed as a weight loss drug. It's bad enough that it's even FDA approved. I was using it for neurological problems. A lot of neurological drugs have bad side effects, so I can understand that. But losing weight is not worth losing your mind. The worst part is most doctors never even mention anything about its mental effects, and as far as I know memory loss is still considered a 'rare' side effect, even though every person I've ever spoken to about it has experienced it.