Hi For me, counting breaths at a relaxed pace is really helpful, and I was also able to use this approach with patients in the sleep lab. I don't remember a single time when it didn't work. Here's a link to something I wrote on breathing for relaxation that might be helpful for you.
https://insomnia.sleep-disorders.net/clinical/breathing-exercises
It's worth mentioning that many people who have undiagnosed sleep apnea often go to the doctor initially with complaints of treatment-resistant insomnia. One trip to the sleep lab and they realize they can't sleep because they're having apneas. If you're treating yours, then you're at least one step ahead of them!
Best, Tamara, community advocate