Hi and welcome to HCM.
You should take it serious but you shouldnt be concerned. You are young and any cancer isnt very possible at your age.There are various conditions which cause stomach pain and bloating
. usually this is gasrtitis, GERD or IBD. It should be primary treated by changing dietary habbits,eat fruit,green and avoid fats, alcohol and sugar. Also gastroscopy should be done to see degree of gastritis
is common at young woman and usually menstrual bleeding and lack of iron cause it. It can be sign of bleeding from bowel wall or tumor
but it isnt the first thing to think of. If you have pain while defecating or opstipation then you should concerned and do colonosopy. If not you should take iron supplements
and change dietary habbits.
Wish you good health.