Hey, thanks for your answer!
Yes, I had barium swallow test, but only esophagus got checked. The doctor didn't order RTG of the stomach.
No doctor suggested hiatal hernia - they did check my stomach manually if there may be one, but didn't find anything. However, I forgot to mention that I've been diagnosed with a cascade stomach. From what I read, hiatal hernia is harder to notice in cascade stomach. I don't know whether cascade stomach is something that I've been born with and it's completely natural for me, or if it is simply a manifestation caused by some other issue that I haven't diagnosed yet.
As for the gallbladder - technically it doesn't seem like it could be an issue for me. GB usually causes pain and reflux, while for me it's rather constant discomfort, belching, and well... maybe reflux since I feel like there is something stuck in my throat. However, some other user reported gallbladder dysfunction after running Hida Scan and their symptom was just annoying belching. I think it's worth checking out with an USG at the very least, and then maybe hida scan if there was something noticed.
Also, one of my recent ideas is to check for H. Pylori again. All symptoms came back 3 months after eradication. I did a stool test twice, but that was 6 weeks after antibiotics. Perhaps it came back false-negative because of this? I will be checking it again with both stool test and breath test.
Thanks for the suggestions so far! I'm determined to find the root of the issue and finally start enjoying my life again