16 Year Old With Pain In The Chest And Shoulder. Need To Be Concerned Abut Heart Problems?

I m 16 years old, 17 in May and I am fit and not overweight at all. I ve never had this happen before, my family has no history of heart problems and I try to stay healthy and eat healthy. I woke up with a slight hurting in my left chest/heart area, but I ignored it and eat my cereal breakfast and got ready for college. As soon as I walked for 30-40 seconds the pain returned but much worse, and it also hurt my upper left shoulder and back areas with along my heart area. I couldn t bear it, it was intense and I had to go back home. Now I ve been sat on my bed for while, it doesn t hurt much, but when I take a heavy breath it gives me a stabbing pain. I did a few push ups to see if the cause was the walking, but it didn t change nothing. Please may you help me know what these pains could be due t?