Sleep help??

I am 99% sure I’ve tried it all by now but figured I’d crowd source anyways. My 4 year old has never slept through the night and I feel like never gotten deep sleep. It’s always very light/dozing off style of sleep. We have tried so many routines and supplements and everything in between and nothing works. He is mildly on the spectrum. Lately it seems to be getting worse and I’m starting to feel a little hopeless. It’s effecting basically everyone in the house how much he is awake at night. My other kids sleep great. Has anyone had a kid like this?? Any suggestions? We’ve brought it up to multiple doctors and we get some advice but nothing that works. I am wondering if we need to do lab work or something next because I feel like we have exhausted most of our options 😭 If you have any tricks or tips please share them 😭