That sounds like exactly my anxiety-sleep problem. The doc who initially prescribed me anti anxiety meds said that whenever a patient tells him that they have trouble sleeping because their brain "won't shut up" or "won't turn off", he immediately starts anxiety screens for them because it is "practically diagnostic".

It helped me a lot -- even just having the meds around, even when I most of the time don't take them! Just knowing they are there and I can make the brain shut up if I need to seems to help it settle down at night.