How to gain weight with gastritis problem? Also have irregular motion, H pylori infected, undigested meterial in stool. I have gastritis problem before for years, I have done indoscopy and doctor suggested me for H Paylori kit medicine and my problem was resolved but now I am suferring from same problem like heavy gas, Chest pain, esophagus pain, publing, don t eat, weight loss. So can, I take tose medicience again? And my Vitamin B12 leval was also down and I have taken injections and tablets also for same. So, please suggest me what to do?