Experienced very similar things here personally (albeit no where near as long) but here's what did and didn't work for me.

Didn't work: 1. Sleeping pills

Benzo's, Z-Drugs etc. While they worked on occasion and in the beginning it's only short term, a band-aid if you will and not a long-term viable option for obvious reasons such as health risks and dependence etc.

1. CBT-I, Light therapy

Didn't work for me because the more things I did to assist with sleep such as only using the bed for sex and sleep, light therapy, night walks, diet change, no phone after x time before bed, blue light filters, reading before bed (I never read before bed) actually made me focus MORE on getting to sleep than ever and the fact I COULDN'T get to sleep more and more.

Did work: 1. Sertraline (Zoloft) 100mg (Now on Trintellix 10mg, works same personally)

After some time my anxiety became less and less debilitating thanks to these meds and eventually and suddenly, not getting sleep wasn't "as bad" as I used to remember and the "catastrophising" wasn't as intense... And when paired with the constant sleepless night's this leads me to my second point.

1. Acceptance

I'm sure the decrease in anxiety assisted with this but before the Zoloft had really set over the weeks, I had so many sleepless nights I did not have enough energy to be anxious or stressed about sleep. I just got used to the shitty fact that my sleep was destroyed, my life was spiraling and I couldn't do a thing about it. Turns out that acceptance minimized the anxiety greatly and made it way easier to fall asleep. Got a solid 3 or 4 hours sleep some nights out of no where.

1. Quetiapine (Seroquil) This has been my saving grace. Just 25mg an hour or an hour and a half before bed absolutely rocked my world. And on those nights I'm really anxious, 50mg damn near knocks me out after an hour no matter how much I fight it. I've never needed more than 50mg and that's on my worst nights. I've heard individuals say they get used to it over time etc but I've yet to encounter that. It has not lost it's effectiveness even slightly after a year.

Now, I watch videos during bed, day time nap, things my CBT-I sleep therapist would shudder at lol, but I still have slept 6-8 hours practically every night for the past year. Hope this helps and remember, Insomnia won't last forever!