5 year olds mouth chewing?

My son is now 5 years old.He has has had about three episodes  that we  know for sure were seizures One when he was four years old was very bad and had a bout 5 seizures within and hour.I dont know what kind but they were all kinda different but most were where he was stiff mainly on one side and jerking movements with eyes open but could not respond .But he also has been doing this thing where when drifting off to sleep like in the car or on my shoulder that he bites his lips so hard that he is bleeding alot.He then has a huge ulcer for days and sometimes cant eat or drink with it.He acts like it doesnt even hurt when he does it but wants the blood out of his mouth.He is fully aware it happend and usually just acts little scared about the blood.I always ask why he did it and he says he cant stop and he has to eat.My son has a little developmental delay so its hard to get straight answeres from him.This is not the normal chewing on your lip or cheek cause your bored..Before this happens he will say stuff like "my brain is smoking"..which is something he said after one of his major seizures.He also told me to turn off the music in my van cause it was "making him sick".What does this sound like?He is on Keppra twice a day and is still doing this.I also want to add before his first "real" seizure when he was 18 months old me and his dad found him laying in his crib starring up at the ceiling not responding and was chewing his lip and cheek very fast and was bleeding .We could not get him to stop.I have brought this up to Neurologist and Pediatricians and never gotten any real feedback.Does this sound like anything?