thoraz, I share your pain. I have had trouble sleeping since about age 25. I know part of my problems are hereditary as my father slept poorly as did his mother before him. Aside from that, like you I have tried many things to try and get a decent nights sleep. On a rare occasion it does happen, when I sleep restfully for 6-7 hours but there is no duplicating it. I have tried keeping records of what I eat, what I do, where I go, ad nauseam, and with no conclusive results.
What recommendations I can make tho are as follows:
You say you don't want to use medications (I feel the same way) but you also don't mention anything about an antidepressant. If you are not taking one, I urge you to see your doctor and ask for one. They don't necessarily or directly make you sleep but they do remove most of the anxiety that we have. And you won't be sleeping if you are anxious. I have been on my antidepressant for almost 20 years now and can't think of life without it. The doc does not need to be a psych, a GP/family doctor can prescribe one just as well.
If you have several things to do tomorrow, don't try to keep up with them in your head. Write out a to do list so you can avoid dwelling on them.
Pay particular attention to your sleep environment. Having the right amount of cover on your bed and regulating the temperature in the room has been one of my toughest challenges. Generally, I can get the right combo once summer or winter has settled in but spring and fall where the weather varies so much makes it much more difficult. This is part of Aspies not being in touch with their physical reactions. I have found that I may not feel too hot or too cold but I actually am because the acceptable range for us to sleep is quite narrow.
Of course, if there is any noise during the night, such as road or air traffic, you will have to start using ear plugs. WalMart has some by Flents that do a great job and are not expensive at all.
A regular schedule helps too. Like losing all screens an hour before you turn in, go to bed and light out at the same time each night, etc. Also do all you can well ahead of even the hour before you turn in, like showering, donning pajamas, brushing teeth, whatever else so that when its time to go to bed, all you have to do is pee one more time and go to bed.
Hopefully these will help but I doubt anything will be a magic cure. If you find one, please post it.
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Your neurodiverse (Aspie) score: 120 of 200
Your neurotypical (non-autistic) score: 74 of 200
You are very likely neurodiverse (Aspie)
AQ = 38 MBTI = ISTJ Gender = Non-binary
I strive not to perseverate. You can PM me for more info.