How hyper is too hyper

My son is also like Perfect's youngest son. He truly CANNOT sit still. Ever. If he's waiting in line his legs are shaking, if he's sitting on the potty, his feet are bouncing. Etc. ALL THE TIME, EVERY MOMENT OF THE DAY.Incidentally, he was also prenatal exposed to stimulants and I've heard that extreme "hyperness" is common with stimulant-exposed kids.