Oh dear, I can see how worried you are about sweet Tate.
Well, I hate to throw another idea out there - but Marcel used to do this back when he used to have "ibs/ibd/colitis/unknown" -- when his tummy would bother him, or he was having digestive pain - he would get in this position to feel better or relieve something. I think it's a posturing that makes sense if there is pain in the torso (like a desire to stretch the area out). He would also lie flat if he was *really* feeling low/bad.
So, it could be related to the LP, but it could also be related to something else, possibly. She isn't having any poo problems, is she? Any tummy noises?
I hope she feels better, Brooke. HUGS to you and the babies.