Fifth disease in and Adult

About 5 weeks ago I started having joint pain (severe),  about a week later one of my children developed a rash.  We both went to the Dr. they told me she had a virus and they told me I probably had Rhemtoid Arthritis. They proceeded to do every blood test under  the sun. With no determining results.  In the mean time she prescrived a steroid (Medrol dose pack) which I took for a week and I felt unbeleivable.  Soon after all this my other 2 children came down with the same rash.  Which after alot of research and asking around I determined it definately was fifth disease.  Now I am still have minor joint swelling in my hands, elbows, feet, and knees (nothing like that first week though).  Now I have the rash.  I itch like crazy!  I guess my concern is that with fifths disease... doesn't the rash usually come before the joint pain and swelling?  I mean it has been almost 6 weeks.  My kids are all over it, their rash is gone.  I have now had the rash for a wk and a half.  It's getting worse.  My doctor seems to be baffled at this and I am starting to feel crazy.  My blood work was fine. I still wake up every a.m. with stiffness and swelling and now the rash.  I am at a loss.  I don't know what to do!  Please help........