I'm now almost 5 months PP and the chest pain is worsening. My sternum, right between my boobs but…

I'm now almost 5 months PP and the chest pain is worsening. My sternum, right between my boobs but closer to my left, feels like a cement truck is sitting on it. It stings when I move too far to one side or stretch too far or breathe too far out. First time it happened I thought it was just because I laid on my stomach, but it's still here. Could it be bruising from pushing and straining during labor since I was having breathing issues during? Should I go see the doctor? Not worry about it?