Over last couple days been having sharp pain on left side if chest below nipple it last 10secs or so and happens mulitple times what could cause it?

Heart: A 40's male with left sided fleeting chest pain should have one concern - the heart. As doctor's we commonly think of the worst, and so as not to miss the diagnosis. See a doctor and have a stress test. This is the most important concern you should have right now. If this is not the problem, you will have plenty of time to investigate other causes.