Stomach problems were my first symptom of B12 deficiency. It started with bloating with evening meal. It progressed to everymeal. I eventually ended up with a severe problem with gastritis with everything I ate. Lasted a couple of years. Lost much weight. I had chest pain too. In the beginning, I couldnt tell if stomach was making chest hurt or vise versa. I did get better with both. Stomach only acts up once in a while. It is pretty much ruined as far as what I used to be able to eat. Like, raw onions. No way now. I just have to be careful. You have to add things back slowly. I sure missed my nightly vanilla breyers with peach schnapps drizzled on top. Im back to it now. So will you. Keep your chin up and take your MethylB12