I have always been a side sleeper. I recently switched to a new machine and to a Dreamwear nasal cushion (switched from pillows). I find that if I try to sleep on my side it pulls the mask off my nose and I end up having to readjust everything. I've gone to forcing myself to sleep on my back but for me this is uncomfortable. Any suggestions?
You might consider getting a Small frame if you are using the Medium frame for the DreamWear. It's a bit more snug and would likely be more stable when side sleeping tends to cause the mask to move too easily.
Going to the Small frame made a substantial difference in mask stability for me.
Also if you haven't tried the gel pillows for the DreamWear you might look at those. They were more stable than the under the nose cushion for me and you have used nasal pillows in the past. All you need is the nasal pillow part because the frame is the same whether cushion or pillows.
You should be able to sleep in any position that is the most comfortable for you and that would be what I worked towards in terms of masks. Not adapting sleeping position for the type of mask.
I am primarily a side sleeper but will usually end up doing all positions at some time or other because I can't stay in any one position for very long due to spine issues.