You have been taking HCl for some time. Has it solved anything? It does not work because the bacteria can cope with it. It's throwing good money after bad IMO. I have cut it right back because it is all wasted because it gets neutralized so quickly. I use mainly Malic acid, at least that is fairly inexpensive and has other benefits such as improving ATP energy production.
A recap on things so far:
1] You believe that you have poor digestion & acid reflux.
2] You are slightly under weight, have skin problems, lymph swelling
3] Your Dr has tested and confirmed Gastritis via Endoscope exam but unfortunately no biopsy was taken.
4] Your Dr then did an antibody test for H. Pylori which came back negative. Therefore your Dr is pretty certain that Pylori is not the cause of the Gastritis.
5] Your Dr most likely has no further idea because there is no other KNOWN cause.
Two symptoms of Gastritis are unexplained loss of weight and belching/burping. Does that sound familiar?
I doubt that your doctor can do much until research proves another cause. The best you can do IMO is to encourage your Dr to find something else. Tell your Dr if you have not already that you have undigested food in your stools and that you believe that you are not producing sufficient stomach acid which you believe is affecting your digestion. Reflux can be a sign of insufficient stomach acid as that Dr Myhill link explains.
Ask for a heidelberg stomach acid test to check your stomach acid production.
After that shows a low stomach acid production. Tell your Dr that you understand that bacteria other than helicobacter pylori can inhabit the stomach, neutralize stomach acid and are probably causing your gastritis. Ask for a stomach biopsy to identify what bacteria are present in your stomach. Your Dr might learn something from this as well. If you can ask just for this without showing any reason, the Heidelberg test, then do it, the biopsy is all that is needed. I don't know how it works with your Dr. If you can just ask for something and your Dr will do it, providing you pay for it, then fine. There is no point in paying for something, a heidelberg test if it is only going to confirm what you believe.
Once your know the name of the bacteria and the strain, because that is also important, then you will have what you require to treat it.
You can then either find someone experienced in treating gastritis, maybe a naturopathic Doctor or healer or make use of the following
Dr Ettinger has experience in treating such conditions. He will need to know the name of the bacteria and it's strain so he can recommend the correct course of treatment. I did mention the need for quorum sensing inhibitors in order to defeat the bacteria, the bacteria name and strain is needed in order to find suitable quorum sensing inhibitors.
The bacteria will signal to one another to do various tasks. One important one is to build/strengthen their biofilm which protects them. They release a signalling compound to do this. It's like they talk to one another saying "Get to work everyone, build, build, build, strengthen our home." What is needed is to send a message saying "Everything is fine, home is fine, nothing needs doing" Meanwhile substances to break up the biofilm can be used and the bacteria do not rebuild it. They are then vulnerable and can be destroyed.
I urged you not to make any attempt to destroy them for a very good reason. It does make them stronger, more resilient and much more difficult to destroy. Many people on this forum try and fail and make it worse for themselves, because they do not know the way to do it. Half hearted attempts with antibacterials and antifungals will always fail. It takes a lot to beat them.
Alternatively you might try shotsee's approach and hope it works. Basically very large amounts of vitamin C, somewhere in the region of 100 to 200 grams per day. It should not cause any adaption by the bacteria. Whether it will work, I do not know. You would not need the name of the bacteria to do this. It will take some time.