What Causes Chest Discomfort?

Hi,my name is ahsan.I have a chest discomfort for a long time,i have seen so many good doctors but nobody could solve it...everybody says that there is no problem...i have done ECG and ECHO color doppler and xray....but nothing is found...i have taked gastric medication also..but problem still is there....it happens and after one or two hours get solved and then again happens,,,this way this is going...what is the problem and what is the solution....i have seen psychriatist also...but nothing improved......pls pls help me...