My 9 month old dd has been sleeping through for about 2 months, roughly 90% of the time. Fed to sleep with a bottle at 8(ish) and up normally about 5:30/6. Sometimes she wakes up with a little cry in the night but the dummy and a face stroke/hand hold gets her back to sleep.
The past 3 nights she has slept terribly. The first of the last three nights it felt like she never got into a deep sleep, crying every 40 mins - 1.5 hours. Second night same thing only slightly better, and again last night. In the end I was getting up so frequently I put her in my bed as I'm shattered (bad I know).
All this is fine and expected, but the thing bothering me is for the last 3 nights when she is asleep in her cot her back is arched and her head also. It looks really uncomfortable, almost a 90 degree angle. She's always slept on her back. If I roll her onto her back she rolls back into this position, she looks contorted and I think it must be uncomfortable. Literally every time she falls back to sleep she's automatically going back into this position, even in my bed this morning 
Absolutely fine in her self. No other weird happenings. I should mention her first tooth came through yesterday so a little grumpy as expected when teething, but also lots of smiles and laughs. She is a little constipated, but on prunes/water which normally sorts it out fairly quickly.
Any idea why this is? Stupidly Googled and the results were severe/have made me worried - sleep apnea/autism/Aspergers to name a few (and that was on 1 page called 'why is your baby arching his back!). GP appointment needed or am I wasting their time?