Hi I'm A 21 Year Old Female, Live A Pretty

Hi I'm a 21 year old female, live a pretty active lifestyle as I am a collegiate softball player. However recently I have been experiencing a frequent stinging in my heart throughout the fast few weeks. I have experienced this sensation before when I was younger but never this many accounts in such a short time frame. No huge changes in my diet or physical activity. The feeling is only on the left side and can sometimes be painful. Any information or insight would be greatly appreciated! Thanks you.