Digestive Issues. Past few weeks)

Hello Doctor I'm 35 years old. I was diagnosed with Iron deficiency ( Ferritin - 6 ) because I had symptoms like lightheadedness, shortness of breath , severe hair fall, low energy and tiredness. So I was prescribed to take (Ferrous sulphate) 100mg elemental iron for 3 months . Post 3 months of taking iron pills , I was experiencing the below, (weekly twice or thrice only if I consume little spicy food) 1)heart burn, & stomach burn, 2)Reflux / Burping / Belching 3)Noises in stomach Above complaints was happening past 2 months. Also I was taking iron pills as well for alternative days with less mg(27mg elemental iron) as told by the nearby Dr to avoid stomach issues. But now, past 5 days , I'm experience 'Severe burn upper back after eating bland foods, burping & noises in stomach but neither front side heart burn nor stomach burn. ( PS- I am not consuming milk , coffee, tea, fried foods, hotel foods , spicy foods, junk foods, refined sugar , wheat products past few weeks)