Hello~It sounds like you may have a hiatal hernia, I say this because you mentioned that you got some relief by shifting your body and having the head elevated helped. Your other symptoms sure to point in the direction of a Hiatal hernia as well. You should you were checked for GERD and had a colonoscopy, did they check for a hiatal hernia? If they haven't, I sure would ask about it.
Hi there, I’m female, 26 also. I got almost same problem. Last December I got reflux twice so I decided to have check up as I thought I have heart problem because of chest pain and very strong pulse. ECG and Utz done both normal. I took medication for reflux, but I got this abdominal discomfort (on and off) most of the time mild to severe (I still dont know the trigger) I mentioned it on my doctor, he said it wasnt normal but he didn’t see any problem as I have normal utz next week will be my follow up check up. I’m really stress on this feeling on my stomach.