What could this pain be?

Ive been experiencing a sharp brief pain in the chest on the left side of my body by my best for the last few weeks or maybe a few months now! ive been to the e.r twice and all the test they were able to take on me were normal and im considerable healthy! Im very concerned because of course i want this stop and im worried that when my insurance kicks in that maybe they would be able to tell me with out having to do a surgery on me.Im on 24 yrs old i have no idea what this could be from i was thinking maybe it was gas after taking some gas x and tums but no relief :( has anyone ever gone thru this or can you give me some kinda comforting advice about what to do.. i notice this come out from no where and it completely ruins my mood ... i dont know what to do!