What Causes Pain And Stiffness In The Lower Rib Cage?

Slight stiffness on right side of mid to lower back moving around the right side . Happens when laying down on in bed, sitting and twisting. I cannot tell if it is my back or an internal ordgan. This has been going on for a few weeks. Now there is a silght ache or cooling sensation on my right side around the lower edge of my rib cage. This is not painful but has me worried. I keep thinking this is a back or muscle related problem because I usually notice the discomfort when twisting or laying in bed. Then I start thinking, kidney problem or liver or gaul bladder . I do not like going to the doctor but feel maybe I should. What type of doctors would take a look at this scenerio?