Sleep apnea: how to improve breathing after sleeping on back

I have sleep apnea, and try not to sleep on my back (I wear a fanny pack and a sleep positioner belt, which buzzes if I move off my side.) Last night, my hips hurt from sleeping on my side, so I turned off the sleep positioner, took off the fanny pack, and slept for an hour or so on my back. I woke up with trouble breathing, and still have trouble 2 hours after getting up. Drinking coffee helps a bit. Any other suggestions on how to get more oxygen in me ASAP? Thanks, Lisa