ive been having the same awful problem....
i was a belly sleeper (cant do that anymore

) and i cannot sleep on my side no matter what i do...i would have better luck trying to sleep standing up!
i talked to my doc about the sleep dilemma, and he told me sleeping on my back wasnt a good idea either...BUT....if i layed on my back and put a pillow or some of the blanket, or a wadded up sweatshirt for that matter under one cheek (and im not talking the cheek on your face) that i would absolutely fine on my back....and because my hips were tilted a little, it would take pressure off the main arterty to my legs, and off my uterus....so i said what the heck....i'll try just about anything!
would you believe i actually slept!!!!!!!!!!
its actually pretty comfy and i can always put an extra pillow under my head if i wanna be propped up too!
i hope it works for some of you ladies too.....
Cara