I alternate during the night between side and back sleeping. This is the CPAP pillow I have been using, though after several nights I will switch back to a regular pillow because my shoulders get stiff.

https://www.amazon.com/gp/product/B01MYOADKQ/ref=ppx\_yo\_dt\_b\_search\_asin\_title?ie=UTF8&psc=1

Leakage isn't a problem. For example, over the last 30 days, Oscar shows my average leak rate as .01 l/min. Anything under 25.0 l/min is considered fine.