I Am 23 Y.o. And Female. I Have Had Pain

I am 23 y.o. and female. I have had pain in my chest (sternum area) and kind of off to the left a little, for the last 3 days. If I bend over it hurts. The first day it was pretty much debilitating I had to leave my work early I never get heartburn so thought maybe it was that and tried two rolaids, did not help. Later on tried two tums, that did not help. It hurts more when I go to sit down or lie down but once im lying or sitting there for a few minutes it calms down. The second day at work didn't bother me so bad, but when I got home it seemed to have been more painful. Today, the third day my chest is not hurting constantly but randomly and when I take deep breaths. My left shoulder started to bother me last night and today it hurts worse, dont know if it is related or if I was laying on it wrong.. Its hard to explain pain because it feels different at times.