I know you said you were backpacking but you didn't specifically mention weight as an issue, so this answer assumes you'll trade some weight for comfort ;)
The LL Bean Pathfinder Sleeping Pad is better than most mattresses I've slept on. I'm a smaller framed guy with bony hips and I sleep on my back and my side. My wife has larger hips and sleeps on her stomach and side. Most of our experience with this pad is on the hard floor of wooden lean-tos.
The short version (the one we use, my shins and feet extend past the end) comes in at 22 oz though it does pack down fairly small. The full size is a whopping 34 ounces and packs quite a bit larger.
It's a self inflating foam style pad so I assume others like it would be similar.