I am 20 years old & I ve been experiencing on & off sharp like chest pain in mg left chest. This also has been happening in my left arm, & left side shoulder blade. My arm tends to feel a bit numb. I have been to the ER about three or so weeks ago, there they did blood work, EKG, & CT scan of my head. All came back normal. What can this be? I also heard it s very rare for a 20 year old to experience heart problems.