Try putting the pillow between your legs AND a pillow under your back.
It helps me. It keeps me from being completely to one side and completely on my back. It may be difficult to keep the pillows in place if you move around a lot but your body will adjust. It took me a couple nights to stay comfy
I've tried that before, I took our body pillow and wedged it bbetween my legs an tucked it underneath my belly to hold it up but it just wasn't comfortable it still felt like my belly was being smashed. Sometimes when the baby isn't up front my fiance can lay his arm down the side of my leg.
I lay on my right side with a king size pillow between my legs and it holds my belly and a regular pillow for my head of course. While laying side ways my husband holds me from behind (=