Hi thanks for contacting HCM... As you are young and no history of taking outside food , so your stomach pain could be from functional cause .... You can have somatitis or ulcer ... Yes constipation also can lead pain... Here are few advise .... - Avoid non veg foods -less spicy foods -omeprazole capsule on empty stomach before meal taken for two week ...(1OD) -Take digene like syrup for acidity -if constipation there you might given laxative .... -more water -Avoid stress -Gas forming food restricted like excess protein, cabbage , turnip , onion etc..... If still no improvement consult physician for examination and further work up done for USG abdomen and x ray like investigation .. Hope your concern solved .... Take care ....