Heartburn????? Please help!!!?

Since yesterday i ate from Mc Donalds in the daytime for lunch... i was fine until the evening....i felt bloated so had a very light dinner...as soon as i ate dinner the pain started it was like a horrible pain on the left side of my chest towards the heart...i could feel the same pain on my upper left back and it worsened went i bent down...today i have been off food..just had a croissant and yoghurt for lunch and now im feeling a horrible feeling on my chestt...it feels like i cant breath properly can this be heartburn i am constantly taking deep breaths which provide temporarily relief..i am 22 years old and a female..my diet hasnt always been good and im trying to eat healthy now