I have sharp pain in right side of chest at times not always while breathing inside ..what could be the possible reasons for this?

Pleurisy?: It sounds like pleurisy, which is irritation to the lining of the lung. It can be from many different causes, including infections. Be seen for an exam and diagnosis.

Stitch?: If this is a knifelike pain when you breathe in that comes suddenly and ends suddenly, it's probably the "stitch" fold in your pleura. A very deep breath ends it. It's harmless if this is what it is, but if you ever feel crushing chest pain or shortness of breath as when you're running a marathon, by all means get emergency help.