Your symptoms are suggestive of
Irritable Bowel syndrome. This is common in this age group and could be triggered by a variety of different things like
Stress,
Smoking , change of work or change of shifts, high fat etc.
First , take a dose of deworming medication like
Albendazole 400 mg. 1 tablet only. After dinner, chew and then swallow. Sometimes a worm infestation is the culprit.
Following this if you still continue to have symptoms - get a stool routine test done to make sure it's nothing serious.
You can take Otiliniuim bromide 40 mg, 20 min before each meal to help with the discomfort. Alternatively
Mebeverine 135 mg 20 min before meal.
Try cutting Tea , coffee,smoking(if you areca smoker) , milk and other fat from you diet for a few days and see if it makes a difference. Then following that you will have a fair idea as to which food you handle better.