Welcome to HCM. Bloating and burning in the stomach is most likely due to severe gastritis. It could be due to consuming pain killers. Take any simple nsaid to subside back pain along with rebeprazole,pentoprazole/domperidon. Antacid suspension will be helpful. Apply nsaid gel locally for back pain. Avoid any spicy,oily heavy food. Take small frequent meals. Drink more water,fruit juices,vegetable soups,buttermilk. Delayed period is usually due to some hormonal disturbances. Keep in touch with your doctor for better guidance and proper medical management.