Excess gas and chest discomfort. Ulcers?

I had excess gas, excess belching and a sharp pain in chest one day when i lie down so i am currently taking dsr in morning and aciloc in evening as prescribed online by a doctor since 5 days. I am currently having little discomfort in chest and sometimes it feels like some gas is trapped below ribs and little belching sometimes. I did a cbc a month ago and found that i had low rbc count and vit b12 deficiency by online sources and i feel it to be true since i do not take milk products and am pure veg so i started polybion l for it and a  month has passed now and felt much better. I have symptoms like shortness of breath, abdominal discomfort, etc. No nausea or vomiting till date. I discontinued polybion l thinking the symptoms may be because of it since 3 or 4 days and started again yesterday night and found some relief, so i want to know that is all the problem related to vit b12 only? And are there any chances of ulcers?