Welcome to the forum.
It would help us to help you if you would tell us what the pressure setting is for your cpap and whether or not you have the cflex turned on. The cflex reduces the pressure somewhat as you exhale; many people find that turning the cflex to its highest setting helps eliminate that suffocating feeling.
The problem is most likely psychological unless you have a pretty high pressure. It is very common to have a problem like yours. One way to deal with it is to use the machine in another room of your house, such as while you are reading or watching the telly, or listening to relaxing music. This way you learn that you can and will breathe perfectly fine.
When you have it on in bed, try using relaxation techniques. Some people pray or use a mantra; I sing hymns in my head. Some use biofeedback and work on relaxing one muscle at a time. Become one with your pap - deep breaths, slow breaths. Remind yourself that the machine is a GOOD thing and your are fortunate to have it. Using it is good for you, good for your body.
It CAN be done. Some fortunate people take to it right away, but for many it takes a lot of getting used to, and a lot of mind over matter. But after a few days/weeks/months you will find that the airflow actually becomes soothing, and you won't even think of sleeping without it.
PR bipap auto sv advanced
Fisher and Paykel flexifit 431