Can't answer your question to explain gas but I can tell you that I just finally got relief myself from gerd (stomach pain, stuck gas, heartburn too) by going full paleo, as in "no starch" either. I was eating paleo with rice but got great advice here to cut it out (see here). I eat fruit, veggies, protein, nuts, seeds, olive oil, butter. Totally worth it to have no more gerd and not have to take nexium anymore either.

Best of luck I hope it works for you too!

I hope you've seen a doctor to make sure the pains you are having are really GERD. Especially now that you are having neck pain too, it could be referred pain from other internal organs (e.g. the heart!) and needs checking out. Furthermore,long-term GERD can lead to a serious condition called "Barrett's Esophagus" and that needs medical attention. Once you check out OK with the doctor, eliminating grains and limiting other carbs may really help. Some people find adding some HCL to their diets helps, too.

The gas problems may be due to gut dysbiosis. A good paleo diet with added probiotics (preferably from fermented foods) will help heal the gut.

The most important thing paleowise is to really do it--half-a$$ed approaches are not going to get you anywhere. And don't give up after a week--there's an adjustment period where you may feel pretty rotten. You can get through it and feel much better on the other side.