It sounds as though your son does indeed have a virus of some kind, though that is beyond my own expertise. I doubt that your own rash is related, though it is possible you (and your other child) have the same "bug." In any case, you'll need to rely on your child's doctor for proper evaluation. The rashes may or may not be part of the overall problem, but most such rashes don't point to a specific diagnosis, so the overall evaluation of symptoms is what counts. You should keep in mind that viruses can cause fevers and lethargy in little kids for some time.
Best.
Dr. Rockoff