Chest pain in different areas of chest?

I have been having slight chest pain usually at the edges of my chest left and right on and off for 2 weeks it is very random and I am in great shape, and can still run around and play sports,swim without it hurting me even work chest at the gym without any pain but it still comes and goes randomly for 2 weeks sometimes my shoulder will feel a slight pain but even that is gone now my worst possible reaction to it was cancer but i have never smoked a ciggerate a day in my life ocassionaly marijuanna but nothing big and even when i did it did not hurt at those times