You may need to be scoped. Scans don't always tell the true story. I imagine you are on omeprazole or something similar? And you are avoiding coffee, alcohol, soda, and trying to sleep with your head/upper body elevated? I think if you can elevate the head of your bed, you will find the gas bubble problem to be better. Are you breathing through your mouth? Do you need a different mask? (BTW, after losing weight, I do not need to use my CPAP anymore! It is great!)
I developed an ulcer 6 months after my surgery - for no reason. The doctor said it might have been a stitch that didn't heal well, I was on omeprazole for 4-5 months. A follow up scope showed that everything is now healed and doing fine, but I did buy a bed with an adjustable frame so I can easily elevate the head. Best thing I ever did (besides surgery!) The weight loss and head elevation completely resolved my gastritis and GERD. Even the Barretts esophagus resolved, which is amazing. Hang in there. Only good things to come for you! A year from now this will all be behind you and you will be a new person with most of these health issues resolved.
PS: It could be that the pressure setting of your CPAP is too high. Have you talked to your sleep doctor? As I lost weight, my pressures were adjusted, until I didn't even need it anymore.