Had this before.
I'm pretty sure I had gastritis, having already damaged my stomach from pain killers for my back (just Ibruprofen)
Started as odd indigestion, then progressed to exactly what you described.
I battled on for 6 months with little to no help. I fell pregnant a month after symptoms started and figured the symptoms could now be contributed to that, I unfortunately lost the pregnancy but the symptoms remained albeit not to the same extent they were in pregnancy.
For that 6 months I took the off omeprazole (kept getting given 2 or 3 weeks worth and tbh didn't have strength in the end to get more help) I did occasionally take a anti acid but all they did was make me burp.
A month after my pregnancy ended I was at my wits end and broke down at my GP. He suspected acid reflux that had gone on so long it caused damage.
I was given a repeat prescription of omeprazole, 4 time a day to start with and weaned down. Also Peptic stuff to take as and when needed on top of the anti acid tablets. A anti spasm medicine was discussed but I declined wanting to see how the above helped first.
I also cut everything out. I lived off plain pasta and water for a week before introducing things back in.
Took about a month for things to settle.
I'm now about 6 or 7 months down the line, my omeprazole is down to once a day (twice a day during certain points of my cycle as apparently common for these symptoms to worsen then, and they do for me!) I eat whatever I fancy, and back to my fizzy juices.
I'd say I'm pretty much back to normal, aside from the odd day here and there but I'd say that's just basic indigestion now as it no where near as bad as it was. My pain before was constant, with major flare ups of it thrown in...now it's just some discomfort occasionally.
GP says it could now just be my stomach will be sensative, says like a external scar... They can get irritated. (scarred lining possibly)
Definitely seek help and don't let it go on as I did, you just get more issues. I don't think it resolves itself..