Hi, Im a 23 year old male, approx. 62 180 lbs.  I have been lifting weights for over a year now and have never had any problems.  Three days ago I was on the bench press doing my normal warm up routine and I heard a loud pop in the left side of my chest.  Following this the left side of my chest and back began to hurt, the pain worsening when I breathe.  I had x rays taken, and nothing was found.  I was wondering if this just sounds like a strained muscle, or if there could possibly be more going on.
HelloWelcome to Chat Doctor. By your description it seems that you have sustained a muscle pull while exercising. This pain seems unlikely to be coming from the heart. You should take painkillers like diclofenac which will reduce the pain and also decrease inflammation at the area. Topical gels like voting gel, diclofenac gel will also help. It will take about 4-5 days for the pain to go. Please give rest to your affected portion for at least two weeks. Wishing you good health. Regards