your pdoc should be able to help. what works for one, may not work for another...
I wonder if your therapist could help you to change/intrude on the intrusive thoughts during the day re: not sleeping at night. Letting go is good---maybe a relaxation exercise before sleep. One problem with anxiety attacks is that they become associated with the situation in which they occur, or first occur, and can be triggered by that fear ---
I have had to deal with severe anxiety and insomnia since my late teens (now, being older, the sleep issue doesn't bother me much, as I do not need the sleep I once did)---I do take medication but wish I had found another route, so I hesitate to suggest a medication; although that may become necessary. Let us know how it goes.