I'm a skinny woman with prominent hips and am also a side sleeper and sometimes a stomach sleeper.

I got pillows from sleep number that are adjustable. You just take a layer out. My partner is a real tall guy who sleeps on his back and he leaves in all three layers. I took one of mine out. I use the two layer for side sleeping. I put the extra single layer into a case and use that for stomach sleeping.

Idk how to fix your mattress but coil mattresses always hurt my hips unless there is a pillow top. I had an expensive tempurpedic that was really good. After a move, I had to start again. I bought a cheap zinus off amz. It didn't have a pillow top but it was like 1/5 the price of a tempur. Been sleeping on it six years now and it's still like new. It's firm even when it's hot here (I live in the south) but still soft enough to allow for hips.