How important is it to get diagnosed early if you have RA?

I started having joint and muscle pain in August.  Was prescribed prednisone for ten days and felt like a new woman.  Pain and stiffness had apparently creeped up on me and I didn't even realize how bad it had gotten.  The doc ran an RA factor that was negative.  Swelling went down, but had chest pain real bad twice.  Went to ER the first time and ruled out heart problems.  Second time, just toughed it out.  Doc finally ran sed rate and crp.  Sed rate came back 18 and CRp came back 15.  Doc still not thinking RA.  Gave 15 days of antibiotic for double ear infection and sinus infection.  Doc also ran 2 Parvo tests.  The one that would show if you currently have Parvo or had it in the last 2 months was negative, but the other one was positive and says "indicated past infection."  But when I read about this test, it says at least 66% of people will test positive for having had a past Parvo invection.  Doc says parvo would cause arthritis symptoms for six months and seems to think I should just wait?