I have the same sleeping issues you mentioned. My Montbell super-stretch bags have 10 slightly stretchy inner baffles which gently hug the bag occupant's body as s/he moves, rolls, tosses and turns; always minimizing the vacant airspace in the bag. The outer baffles expand to allow stretching, sitting crosslegged, etc.. I got the Long bag so I have a LOT of freedom of movement. Depending on your budget, Montbell sells "UL" 750 fill power, 600 fill power, or cheapest of all, synthetic; all with the patented super-stretch system. Don't get the "Alpine" versions, they do not have outer baffles, only inner ones. (unless 1/2 the stretch is OK with you). I suppose many companies would like to copy this system, because minimizing internal airspace is one variable in making a warm bag, but MB has the patent. I will never go back to a non-stretch bag again. By the way, all their bags have a cinch cord around the lowest baffle, so the bag can be cinched off for short occupants, with the end of the bag optionally tucked IN, to keep feet extra warm like a big down foot-pillow (ingeneous). My 5`3" friend also uses my long bag and says it is amazingly comfortable and warm. I have a #7 long, and a #3 long.
Research these on line, they are highly rated, and deservedly so IMHO.