I need to understand

I need to understand the effects of RA because I don't seem to be getting it. One day I feel fine and the next several weeks it hurts to walk or use my hands. I'm only diagnosed recently and have only started to get pain in my knees, feet, hands, wrists and spine.  It started out with just my middle finger hurting...probably from too much use driving along the freeway (HA).  Anyway, I've tried most meds and am on Imuran now and only been on it 2 weeks. I want to go exercise like I used to...was up to 2 miles on the treatmill, now I can't even walk for too long! I hear and read so many different things about RA that I don't know what to believe. I just want to understand!