Light pain in right lower chest. Issue?

Hi, I am facing chest pain in right side lower part since 1 and half years. I visit the doctor minglani. The pain was like heart beat in right lower chest. Doctor said it can be some infection and he recommend me some expensive medicine for 2-3 month which I completed. After few month it felt again the same after having meal the chest pain like heart beat start in right side then I change the doctor in metro hospital he also recommend me some expensive medicine for continue but did not tell the problem. I took medicine continue for 2 months and leave it. It has been around 9 months. Now my chest pain again but now it's like someone putting niddle when I take breath. I am very tense and don't understand why it is happening and why doctors don't  tell the problems exactly.. I am stressed for this reason. Pls suggest what problem can cause this issue