I used to sleep on my stomach most of my life, too. But when I started seeing my chiropractor, he convinced me to start sleeping on my back and I was able to get used to it within a few weeks. The key for me is putting a pillow under my calves to shift the angle of my pelvis. Without the pillow, my back arches too much and it's painful. Do you get interferential electric muscle stimulation ("electro-therapy") after the adjustment? I think it's mostly used for sports therapy, but it helps hold an adjustment if you do it right after.