Otc drug symptoms and conditions

I have been on Lamictal and Topamax for approximately 4-5 years now. I also take effexor. I have a seizure disorder. At first everything was alright, however now I have been having double vision, staggering, memory loss that has occurred slowly within the last two years or so, and of course as with most meds the usual diarrhea or constipation. I wonder how long does it take being on medication for these side effects to kick in? I read all literature whenever I start a new medication even if it is a OTC drug. (over the counter). I just got out of the hospital and am being sent from one doc to another. I feel like a guinea pig in a lab! Please help!