What Causes Pain In Mid Chest Area And Back While Breathing?

Hi, I m experiencing some pain in my mid chest and back. It hurts to breath deeply and move at times. I get these feelings every so often after waking up where it feels like i slept with a weight on my chest. They would originally go away during the day or at least by the next day that I at first assumed I was sleeping funny. But now this has lasted for about 4 days, and it feels like someone punched me in the chest and my breast bone is bruised...and I can feel an ache between my shoulder blades in my back. I haven t done anything in the past couple months that could lead to this. I m a full time student and I work at a desk job, so I don t really have the time to go to the gym or do anything to active. Thank you.