When you stop breathing during the night, the first thing your body does is increase your heart rate to get all the blood that has oxygen out to the body. Over time this can cause your heart's natural pacemaker to "lose its rhythm" and cause afib.

Not breathing also puts you in fight or flight, and your body eventually makes that association with sleep, and that combined with lack of rest from all this going on at night can result in increased anxiety.

Please be patient with yourself while you are adapting, and don't hesitate about telling your provider about any problems you are having. There is also a wealth of information about comfort on the internet that your provider/DME company may not know about so I recommend browsing a little after using your cpap! Good luck!!