Try this position it's less energetict, as he is not having to support him self, or lift his body weight to thrust.
You lay on your side, with the lower leg straight down, lift your upper most leg, and bend it at the knee. He then straddles your thigh and hitches forward to get in you, he can then hook one hand under your raised thigh and put the other one on your lower back to give him something to steady you as he thrusts. This will also help if he has weight around his penis; as your bum pushes his flesh back against his body as he pushes forward, giving him a bit more length to work with, plus he gets to not be on the bottom.
This one I think is called the x position because your bodies form an x shape. You lay on your back, lift your legs, he lays on his side at 90 degrees to you,and moves up to you until he is in you. You can then bring your legs down from the knees. He just stays on his side and rocks backwards and forwards. If you need to put more force into it, just take each others hand to pull against.
This variation of spooning is good, you lay on your side and pull your knees up, as far as you can, and straighten your legs out a bit from the knee. He lays on his side his legs along side yours, one hand on your hip. You are now in standing doggy possition; only laid on your sides.