Differences between OA and RA pain

Hi, I was wondering if it is possible to tell which condition between OA, RA and Fibromyalgia is causing the pain and weakness in my knuckles. The pain feels deep in the bone with a little swelling around the joint. There is also stiffness and tenderness present. I am right handed and this is currently present in my left hand only. I have confirmed OA and Fibro, and currently being investigated for RA. Many thanks for your help.