I'm 20 i've had a chest pressure/tightness in the center for more than a year already. seen many doctors that tell me i have nothing. what can i do?

Pain: with with the think that you are 20 and the description that you give I would suspect that it could be Osteochondritis which is an inflammation of the ribs were the attached to the sternum I would try and anti-inflammatory such as Aleve or ibuprofen and see if that helps

Low quality service: does not help troubleshoot; promotes what insurance $ will reward; http://goo.gl/Blh6rW. Primary medical decision maker=always yourself. Most chest pain=not heart, especially at your age, but chest wall, etc. Yet from autopsy studies in US going back >8 decades, artery disease present in 1/2 of US population by age 7; no symptoms for decades because in wall; arteries enlarge in precise proportion.