Is it normal to sleep with my arms in the air?

I have a history of night terrors and nightmares, and I take medication to help control them. The medication is called Prazosin. I take 6 mg at bedtime, which is a fairly high dose. I weigh 105 pounds and am 40 years old. I am bi-polar with severe anxiety and panic attacks, with which I also take medication for... With that being said, over the last several months I have developed some very strange sleepy patterns/habits. I'm curious to know if anyone else has experienced this and can help me! My husband tells me that I shout in my sleep.. Ok, that is better than when I used to scream... Now I don't move at all. I fall asleep in a position and that is how I stay until I wake up in the morning. The part that has me concerned, is that I typically fall asleep on my back, and I am sleeping with my arms in the air. Not straight up over my head, but as if I were sitting and had my arms on the arm rest. I sleep like that, shouting, all night!! When I wake up, I am in pain and am very stiff and sore. It is very hard for me to move and my muscles hurt constantly. Has anyone ever heard of anything like this before? It freaks my husband out, he has video taped me and after seeing the video, it scared me as well. I talked to my therapist about it, thinking that maybe it was a side effect to one of my numerous medications, and it is not. Or at least not that she has ever heard of... On the occasion when I don't sleep on my back, say on my right side, my left arm is in the air. And vice versa. I have restless leg syndrome, and take medication to prevent that and muscle relaxers, nothing helps this crazy sleep position and shouting. I talk in my sleep, most of the time he can't understand what I am saying, but when it is audible, it is usually, "Get away, leave me alone, don't hurt me." childhood issues. My husband loves me, but I know that this bothers him, and it has become an issue for me as well. Can anybody shed some light on this? I know it's not normal...Help!!!