You have developed musculoskeletal pain
as a result of pull on the fibres of muscles and ligaments due to your work out regime or it could be costochondritis
which has got worse due to work outs. Though painful, these are harmless conditions. Since your ECG is normal and your heart looks great, get a xray chest done to rule out any lung condition. Take some pain killer like Ibuprofen
, apply some local analgesic
gel and do some hot water fomentation. Avoid any kind of exercise for the time being.