Agreed. I lean my arms/head against the wall at the head of our bed which takes some of the weight off of my pelvis. A pillow under his head, but not your knees, will help raise him up to a good position without you having to spread your knees too far which can be a strain on the thigh muscles.

Initially this was a difficult position for me more because of the mental part of it than the physical part. I didn't like it because I felt...like I was topping I guess. If this is part of what you're uncomfortable, there a few things to do that may help. He can tell you that he doesn't care if you like it or not, that he is doing it because HE likes it. It may or may not help to have your hands bound depending on your physical comfort/balance, but I like it. You could also wear nipple clamps with a chain that he can pull to remind you who's in charge.

Having said all that, though I like the position more than I did, it is not a position I can orgasm in. Hope some of this helps.