Welcome to NeuroTalk:

I see a few things in your complex experience.

1) please get your B12 actual level. Lab ranges go down too far into the 200's etc and are outdated today. Your lowest normal should be 400pg/ml or higher.
Since you were treated for H. pylori..I assume you take acid blocking drugs? Those lower B12 over time significantly.

2) Flagyl is a known causer of neuropathies. Most people recover over time...but it may take a year or 2.

3) Being scoped... we have had some posters here who developed upper body pain, in the neck and back after endoscopies. This may be due to the mechanical trauma of them or because sadly, statistics show the instruments used are often contaminated from previous people. Up to 30% is the latest figure I've seen. So you could have some new unknown infection.

You could try to re-establish your GI flora with probiotics. It may help. A good food source is Kefir... and Lifeway brand has 12 different strains in it! (more than OTC capsules as a rule).
Having a serving of Kefir each day may help restore some of the beneficial bacteria killed by the H.pylori treatments. Lifeway is available in many stores now. I get ours at Kroger's.
http://www.lifeway.net/

And lastly...did you get any vaccines, before this started? If so you may have a vaccine reaction. Those are very unpredictable.

Getting going with a program to possibly help yourself here, involves as much information you can provide to show what is causing your issues now. Some may respond to supplements, but others less so.