What Causes Pain In Back, Head And Chest In A 12 Year Old?

My 12 year old has been hurting with a hard to describe pain, sometimes in joints, sometimes in other areas just as back, head and chest. Been to ENT, family doctor and Rheumatogy doctor, just recently told that it most likely is a virus even though nothing shows up in bloodwork. She has been sick since Nov 15th 2010. I am so scared and frustrated. Any ideas??