tinks, think of it as a hamster on a wheel, stress, worry, bad adrenaline kicks in, thinking all the while i won't get a decent nights sleep, round and round, so you have horrible broken sleep, that is if you get much at all, makes the stress, anxiety much worse. so on you go, round and round, i am talking from experience. You have to break the cycle, and honestly i do not think you have been well advised to take beta blockers, there are better medicines out there and not sleeping pills.
Counselling is a good start, and better anti anxiety, depression medication, combined they can really help. I know about the trembling, heart seeming to be going haywire, it's is truly awful.