Yup I also use similar u shape pillow recommended by M and Anonymous. On some days strangely though, using it makes my back ache more. So just be in tune w your body, certain days the pillow is useful while certain days it’s not . Not sure why.
What always worked for me however is placing a flat, low pillow at just below knee area to support the weight gravity (=pressure) coming from my heavy tummy. You need to observe your own body, play around with different height pillows to cushion at different parts of your body to experiment what is most comfy for u. Sometimes it’s at your back, sometimes buttocks, sometimes legs.