What Causes Left Sided Pain In The Neck?

i am an 18 yr old male and the past couple of days i have had a bad constant pain in my neck on the left side that felt almost like it was behind my collar bone. Breathing deeply, laughing, belching would cause more pain. today i woke up with a bad pain in my chest near my heart. It has been getting worse as the day goes on. what could this be?