The doctor will almost certainly have recommended "sleep hygiene" (including things like a dark and quiet room at night, not staying in bed when your mind is racing, don't use your bed for non-sleeping activities, try to wake up at the same time every day), light therapy, and melatonin. That helps some pople, but many (maybe most) people it doesn't help and in that case you are considered untreatable. The vast majority of sleep medicine is focused on sleep apnea at this point and it sounds like this is unlikely to change any time soon.

For anyone with circadian issues, the Circadian Sleep Disorders Network is a patient advocacy group that has some helpful info:

https://www.circadiansleepdisorders.org

There is also an independent mailing list mentioned on that site for people with circadian disorders. I'm not sure what similar resouces are available for just insomnia.

Edit: Oh, there is also "Cognitive Behavioral Therapy for Insomnia", which is a structured approach to "sleep hygiene".

Edit2: My overall impression with insomnia is that things like racing thoughts or caffine keeping you awake can be treated but if you deal with all of that stuff and still can't sleep, there is no treatment (and often circadian issues are involved).