please help! :(

Hey everyone..so frustrated today. I called my doctor to set up an appt to talk to him and maybe get a sleep study done. I was up every half hour last night with my heart going fast and my breathing feeling laboured. .even after taking a beta blocker (and ive been taking a whole one everyday)
What I do notice is- the pounding only happens once I actually fall asleep. Once I wake up and lay for a bit everything returns to normal..then I fall asleep and wake up to it happening all over again. Could my thyroid nodules be constricting my air passages and causing a sleep apnea type situation? Also, why wouldn't the beta blockers help? They help during the day when im awake but do nothing for this issue.
I'm really at the end of my rope with this..I dread going to bed at night now and feel like junk all day long.
I keep saying I wake with a pounding heart..but realistically my heart is only beating from about 72-85 bpm during these episodes when I awake..it's not crazy fast but fast for a resting HR and it feels uncomfortable and my breathing is also uncomfortable (can't really explain it)
Any ideas at all? I know im going to see my doctor soon but he never seems to have any idea and maybe I can give him some clues to what it could be. I'm so desperate to just have a normal nights sleep again.

SC..I do have reflux and gerd..and i will say that the slight pounding started after eating (had soup and a little bit of salad) and I did have stomach discomfort while awaking for the first few hours. ..but u think it could cause me constantly waking all night long? And like I said it gets better once I wake up but starts again once I fall asleep.
I do prop my pillow and sometimes it seems to help but not always. I do have to get in with a gastrointestinologist though