Sounds like you could be feeling anxious about feeling anxious :-) You have checked and know there is nothing "actually" wrong, I would get standard blood tests with your primary care guy, make sure you aren't deficient in some vitamin/mineral or hormone and then start fighting the symptoms with "logic". If you have no literal reason to have panic attacks or feelings of dread, make fun of them and shift your concentration (as often as it takes) to doing something else. When I have sleeplessness, I get up and eat a bowl of cereal with a banana (mostly for the milk to help with sleep :-) and "play" online for a bit and then go back to sleep. Often I find my problem was I had to go to the bathroom or turn the thermostat up or down, or just wanted some comfort food.

Do you have a therapist to help with discussing and working through the anxiety? Therapy really helped mine; I still get anxious but can deal with it much more effectively and it is never a show-stopper anymore.