Hi, I'm Having A Tiredness In My Chest Since January

Hi, I'm having a tiredness in my chest since January 18th. I've been to the ER had EKG's and blood drawn for tests, everything came back negative for the unexplained chest pain. Went to my Physician again no reason why and referred to the Cardiologist. Again, no reason from the cardiologist for the unexplained chest pain. I haven't had chest pain in about a week and a half until yesterday. My question is why am I having this tiredness in my chest?