I have chest pains why?

so im a 15 year old female and 2 days ago i starting getting this sharp pain in the upper left side of my back and it sometimes shoots down my arm , sometimes its on the upper right side of my body . but that just started today . it last for a few seconds then goes away on either side .. comes Again a few minutes later . like i said its a sharp pain like a stab /jolt and it deff stops me in my tracks . i don't think its anything serous but i just want to know ur opinion . thank u and have a wonder full day :)