sometimes this happens to me. it's not made up in my case. i have back pain from time to time and lying in one position too long when i'm lucid can pull me out of a dream.
i have this awesome topical cream with GABA and magnesium in it and i often apply it before i go into dreaming. it's by biotronics (i think that's the name). they make a few more great creams. another one with devils claw. they have very little odor so are nice to use in the middle of the night or whenever...
that has really helped me wild or dild and stay in there.
warmly,
bg