Is it possible that you don't sleep well or sleep and wake up every few hours? My uncle has a thing called sleep apnia (not sure if that's spelled correctly), and it's where he wakes up lots of times in the night but he can't remember it. He went to a sleep lab where he got diagnosed, he now wears a breathing mask to bed and thus can sleep through the night without interuption.
If the above is not the case, perhaps you're not getting enough you time? Where you leave the children with a trusted individual for a little while (an hour or so) and go do something that you enjoy, so you get rejuvinated?
Aspies vary in energy levels though, same as everyone else.