hello ,you are very young and your symtom show that your chest constant pain or different may be cause by the heart artery disease ,although you have not the shortness
of breath or any other symptoms,but your chest paint constant 4 years,my suggestion is that take a examination of the heart ,the chest test MRI or cardogram check are the
best choices for you .It is the very important thing for you to go to the hospital,and see the heart expert doctor ,pay more attention to you health.
It may be gas related but if i were you, i would do a chest MRI to rule out other chest related diseases like cancer. (not scaring you but 4 years is a long time). Schedule a chest test - MRI or an xray.
Does this happen after you eat? Do you lie down after you eat?