I did experience something similar during my late second tri and whole of third tri.
I avoided lying on my back when I rest or sleep and slept on my sides. By third tri, I also felt suffocated even lying on my sides and there wasn't a good position to sleep in.
Usually by then the uterus and baby are heavy enough to press on the large blood vessels located on your back and that causes restriction of blood circulation. You can try elevating yourself with a pillow, pregnancy pillow or long bolster. I used a long bolster to elevate my torso even when I slept on my sides.
Hang in there mama! It does resolve after pregnancy.
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