Keppra Side Effects???

Hi everyone. I have a 7 year old boy. He started having pre-seizures within 12 hours and then grand mals within 24 hours of his 6 months of age vaccinations. 2 years old uncontrolled seiures anytime he had a seizure, and then he started having sporadic ones that were the worst he had ever had. He had a grand mal that lasted over 20 minutes and took 2 doses of diastat to get it to stop. We were in the ambulance and at the hospital before it stopped. He didnt wake up from post dictal for several hours after that one. They finallty found something on that trips eeg, and now he gets keppra. He has been on it for 5 years now and has been seizure free the whole time. Yayyy! However, the side effects are bad. In the last year, he is having a terrible time with sporadic short term memory loss and especially word recall. He is studdering severely, tripping over the same word 50 times in a row kind of studdering. Then he gets frustrated, starts to cry and says he cant remember the next word he wants to say. Its getting so severe he can barely speak to me. This all started two days ago. I finished a bottle of his keppra (levitiracetam, its the generic keppra) and opened a new bottle. It was filled on the same date in January. I get several months filled at a time for him, so this bottle was from the same refill as the last one. HOWEVER, about 6 hours after his first dose from that new bottle, he started this stammering and memory loss thing. I find it super suspicious, I cant help but think this sudden worsening is something to do with the bottle. I know that Walgreens sometimes gives us different brand names, so I wonder if its something to do with that? I feel so badly for my baby. He is truly suffering. He is so clingy now so I know he is super upset.