Flu, chest infection, really really bad pain on side of chest?

Hi took the flu end of november, then took chest infection straight after, a week later pain on the left side of my chest under my ribs, the dr told me it was pulled muscle, now a week after i thought it had gone i now have severe pain on the left side which a few times today feels like stabbing pain, it appears ibuprofen isn'tt working, the pain is constant and so sore to cough although when i do the phlegm is white? any ideas? thanks