What Causes Rib Pain When X-rays And Blood Tests Are Clear?

Hi, I am 28yrs old, and i am suffering from right rib pain for past 2.5 months. The area of pain is the last bone on my right rib. I have got X rays and other blood tests done to check any infections, but none was diagnosed.There is no swelling or any kind of mark to identify the area. And normal health seems good. I am 28yrs ols, recently married, with 5.2' height and 65kgs weight.