I struggle with gastritis periodically and once a year on average I also get incredibly painful SI and stomach ulcers.
What worked for me brilliantly and consistently was and is DGL Licorice! I swear by it!
Next, a bit less effective but also helpful - Sanogastril.
Third, Ranitidine - this one I only use when an ulcer hits me out of the blue (mostly because I cheated with the diet).

Diagnosed with AS at 30, HLAB-27+, struggling with chronic IBS since I was 10, still learning how to cope with both...
Meds: Sulfasalazine, ZnCarnocine, Digestive enzymes, probiotics