I'm assuming your psychiatrist would warn you if your meds were somehow screwing with your REM. I'm assuming that is not it.

It sounds to me like you are probably just sleeping a lot lighter due to the uncomfortable and unfamiliar machine and new sleep position. You are probably waking up too often to enter a deep sleep. When you don't get enough REM, you start snatching it wherever you can, even in short spurts while just dozing. I had the same problem when I started wearing a mouth piece to keep from grinding my teeth. I was uncomfortable, and found myself just lightly dozing all night.

Like Wavygravy suggested, you probably just need to get used to the machine. I have heard some machines are more comfortable than others. Maybe you could try a different style?