Topomax and Keppra

My son was prescribed Keppra, the doctor has increased it to the max (he is 3) but he is still having seizures. Today the doctor put him on Topomax, and will wean him off Keppra. I  am really frustrated, and so is he. I am scared of the side effects he might have. He already has side effects with the Keppra as it is. Behavior issues at night which is when he has the most seizures.