pernicious anemia and gastritis?

I was diagnosed with pernicious anemia last week and got my first B12 injection today (Im due to have 5 more over the next 2 wks then 1 every 3 months).  What I want to know is could this be the underlying cause of my stomach problems.  Ive been suffering with nausea and stomach pains for the past 14 months and after several tests including an endoscopy I was diagnosed with gastritis and told I probably had IBS as well!  Im on the same medications as I have been for most of this time (includes lansoprazole,domperidone) but have seen little improvement.  I think I read somewhere that pernicious anemia can sometimes be the root cause of gastritis and if so Id like to know if its likely to improve now that Im having B12 injections regularly.  I know that other autoimmune disorders can be linked and I had a sub-total thyroidectomy 20 years ago and have to take 125mcg of thyroxine daily.
Anybody with similar experiences or advice please?