Ever since I had GBS I routinely measure a temperature from 99.4-99.1, depending on time of day, even when I feel completely normal (I used to always be a 98.6 girl). It could have to do with the GBS – I can’t imagine another reason why it would change like that, otherwise.
I wonder if the return of your fevers is your body’s way of telling you to slow down? Try to rest up a little bit more – have you been under more stress or pushing yourself lately? I’m glad the doctor is checking all the possibilities, but it can’t hurt to try to take it easy.
Good luck with your testing!