Well ..you need to have food on time..do not wait till hunger pangs.....maintain proper time.  Divide your meal time to small proportions so that you dont over eat..secondly drink lots of water. ..atleast 8-10 glasses per day . thirdly.. You need to stroll for a min of 15 min after each meal...stress,tension,all these are also factors of acidity...avoid outside food,junk and oily food...better to have gone cooked food for few days..lack of proper reason also leads to stress zusing gastritis...yes left arm pain and chest pain in your case is due to gastritis only...thank you