We can't get no sleep

I know the title is not grammatically correct- but it is the truth. Why is it so difficult for Robbie to sleep? He was a great sleeper- (WAS should be capitalized) For the past few months sleep has been extremely inconsistent and sporadic. If he doesn't nap- chances are he'll fall asleep early and wake up in the middle of the night- and stay awake until an hour before we all have to get up. Lately -even with no nap he'll stay awake most of the night. Staying awake for him is running up and down the hall, talking loudly (making no sense), jumping on the bed, kicking anyone next to him, and stimming excessively. This will occasionally wake Lexi up and the cycle continues between them until early am. The neuro-ped had suggested melatonin- natural supplement to enhance sleep. I don't think it's working. Right now he sleeps- probably because he's had less than 8 hours of sleep in the last 48 hours. I just hope and pray he sleeps through the night. Mom and Dad are tired too! :)