I have the same problem. I seem to stop breathing or something while lying on my back. I have never found out if it is my asthma or something else. if anyone ever figures it out I would love to know.
Your problem is identical to mine. I too only had the attacks on my back. Then I started to have them no matter what position I slepted in. It seems like you are in a dream sometimes does'nt it. What wakes you is the mucous that backs up into your throat while you are asleep. I bet that you slobber alot just when you are falling asleep. Put to bricks under the head of your bedpost. This elevates your bed at the upper part of your body. Your bed in that position is in a slant, so your body will be in a slant no matter what position you lie in. That's why if you notice in hospitals how the beds can be in a slant position if you choose or not. Each brick can be 2 inches or more.
For starters, you can have severe reflux and not have any taste of acid; I did, from Amiodarone that caused me to wake every 15 minutes all night and never get any real rest. You might try elevating the head of your bed on some rafters to see if it helps. You could try some OTC GERD meds to see if they help. Secondly, you do not have to be overweight to have sleep apnea. This is a common misconception, even among physicians. You don't say exactly how long ago your sleep study was, but it sure sounds to me like sleep apnea. I am not a physician but am an RN. Sometimes the sleep study was not well done, or read incorrectly. Did you actually spend any time on your back at all during the study? I had one once where the girl actually woke me to turn on my back to see if anything showed up then. Sleep techs and physicians are getting a lot more sophisticated today. If you haven't made much progress with this doctor, then get another one! Try a board certified sleep specialist if you can find one. This is not to say that maybe you are having anxiety attacks during your sleep. I don't think it is uncommon.
Hope this helps!
Just want to add that I thought I was the only one to ever have this problem. I could never get much info on the problem nor ever knew anyone that had the problem. Now I read your post and it sounded so much like what I went through. I been on a number of anti-depressants over the years. Maybe it corrected much of my problem. Who is to say though. But, I can very much sympathize with you on the sleep problem. I hope you find some answers to the problem. Just wanted to share my story with you and let you know you are not alone. This sleep problem is a very real and frightening thing. I have always been a rather anxious person, so I do believe my problem was panic attacks in my sleep. Take care and I hope you can solve this problem. So, you can get a good night's rest for a change.
I cant diagnosis you of course, but what you talked about in your post, sounded very much what I use to go through. At the age of 12 the problem started and remained with me for about 30 yrs. Usually about 90 minutes or so after falling asleep, I would wake up feeling as if I was choking and my heart pounding as if it would explode. The feeling was so awful, I would totally freak out. I would experience these attacks maybe 4 to 5 times a week. Some nights I would have several attacks. I too did not have sleep apnea. Nor have I ever been overweight. Doctors have told me my problem was panic attacks in my sleep. In recent years the problem has gotten better. But every now and then I will have one. I have even woke up with this choking and heart pounding, be half asleep, going running for help, throw covers in the floor and finally totally wake-up. Then I would feel like some crazy fool. But the sensation of being asleep, then waking up to choking and heart racing, was truly a very frigthening thing to me. I remember for years dreading to go to bed. Afraid of having one of the attacks.