Hi Andrew,
It could very well be a virus. I live in Michigan and the viruses are running rampant since the kids have gone back to school. I had a low grade fever for 6 days and generally felt like crap. I had other flu-like symptoms ie aches, congestion, sore throat. Went to the dr. and he said it sounded like a viral fever. Since I'm not a fan of antibiotics, I thought I'd ride it out, and I think I'm turning the corner. I know you just finished treatment not too long ago. I'd be a little nervous too, but it could very well just be a virus since it's that time of year. Hope you feel better soon.
Kelley