I had this problem with the mattress I just replaced. It was a softer memory foam mattress and my hips sunk in when I slept on my side, pulling me badly out of alignment. I can’t even describe what it did to my back when I slept on my stomach. I’ve had years of lower back/hip pain that can at least partially be attributed to the mattress. It sucked.
I’m now sleeping on a medium-firm latex mattress that gives me fantastic support. I’ve added a soft latex topper for a little more plushness and contouring support around my curves. What a difference! My back is in alignment as I sleep, and I’m not waking up in pain, even after sleeping on my stomach. So yes, absolutely I’ve noticed that pain. Is your current mattress still hurting you? Or have you found an answer that works for you?