Back pain. please help!!!?

i am male 31 years old. i have tried to search for the answers to my back pain but no luck, i really hope that i get it here. Firstly the area of pain is in the upper back on the left hand side, next to spine and almost exactly behind my heart. now it all started about 19 odd years a ago while i was doing squats, that i felt a sudden current in this area put no pain. Thereafter i use to get the sweet itch in the same spot occasionally which used to go away by scratching it a bit hard. now there on, it started building up a sweet pain + itch and then intense pain + itch and then only pain and then it became a continuous pain without any stops. i used to put a tennis ball at the back while driving to get a minute of relief. it has been a chronic pain torture. Past one year the intensity has increased and i can feel the pain in the spot while i breathe in. At times i feel to cut my effected muscle from the back. i have been to a lot of doctors and all i get after 100 K tests is pain killers. They say it’s not cardiac it’s muscular but no permanent solution. Desperately waiting for a reply.