Stomach pain. Pain? can jt be cancer.

Hello Doctors, Good evening to all, I am having pain in the upper left abdomen below ribs. this pain starts after some times of walking ..or standing for long..my stomach feels like full of air..but nothing comes out.. this is happening from last 1 year..i went to doctor he told me to.do sonography but all came normal.. expect very slight swelling in liver..he said it is okay not a problem..may be gas..he gave me some medicine for gas.. but i am still not feeling okay..this pain is very bad..im not having proper stools..i have to take pet safa churn only then i get some relief..but my pain is not getting cure.. recently 2 months ago i again had medical from my company including sonography..they said all okay including sonography.. pls Doctors help me..why is this pain ? can jt be cancer..pls help me Doctors im worried..i don't drink and smoke..only thing is im overweight..im 94 kg..and according to my height my wt shud be 76.. pls help me Doctors thanks