I had a period of time in my life when I worked at toxic place and my stress levels were so high I could not fall asleep at night. I would have constant flow of thoughts and was laying in bed for hours with sleep not coming. I could not leave that place for some time (circumstances out of my control). I found an article about a method some RAF pilots used during the war to fall asleep. Can't find that particular article I have gone through but google yields lots of results:

https://www.google.com/search?client=firefox-b-m&sca_esv=a6b.....

I tried that as last resort before going to GP but luckily this method worked for me. Later when I left that toxic place the sleep came back on its own.