Okay, diagnosing RA is actually very difficult.  Most doctors look at the test results from many different tests before they will give the diagnosis of rheumatoid arthritis.  Do you know what test was run when you were given the diagnosis of RA?  Do you have any of the symptoms?  I have included a link that will give you some of the symptoms of RA. Here it is:

http://www.healthcentral.com/rheumatoid-arthritis/causes-000048_4-145.html

If you do have these symptoms, then you owe it to yourself to get a second opinion.  Unfortunately RA can cause damage even when you are not in pain.  Please take a look over the symptoms.  If you feel you have some of the symptoms then you can talk with your primary physicain and express your concerns to him.  And if he doesn't want to do further testing, then I suggest you get a second opinion.  Good luck and best wishes!