I hope this post doesn't sound patronizing as that is not my intention at all. I can definitely relate to the frustration you've described, but for other issues. Based on my own anecdotal experience, it's quite unlikely that you've exhausted all the possible solutions. At the very least, you don't have much to lose in trying one new thing.
I found a surprising source of motivation in books about the Eastern Front of WWII. I figure that if Soviet soldiers managed to survive in those circumstances, I can stay calm and collected in much more favorable conditions.
I decided I couldn't live that way, so I worked on breathing techniques like this. After a couple of weeks, I could finally focus on breathing long enough to fall asleep.
I still have nights where it just doesn't work, but it's made a big difference in my life.