When I was diagnosed with sleep apnea, I was not overweight. At least a portion of my apnea is central sleep apnea, which has nothing to do with being overweight, but how my brain does not communicate properly with muscles that control breathing. So just because you don’t have obstructive sleep apnea doesn’t mean you don’t have sleep apnea.
I have worn a CPAP machine for at least 10 years now and have had no difficulty adjusting to it. Have you tried one?