If there is one thing I can recommend you - get the Wellue O2 Monitor. This wil montior your O2 saturation through the night - if the saturation is dropping, you know that there is an issue, irrespective of what the resmed cpap claims. The resmed cpap figures cant be trusted imo.
But once you know what the saturation levels are, you can try a LOT of things which might help. Different cpap masks, head of bed elevation, mouth tape, neck straps - what you end up using will depend on your condition. But imo - dont rely on doctors to diagnose and fix you - you will have to do it yourself. Fortunatately there is a ton of people who are trying things out in reddit and extremely unlikely that you have a conditoin which is not fixable.
Just keep at it and track it using the O2 ring and try out what works for you.