How and when and if you herx depends on a few things - your overall bacteria load (how many infections you have, and how high your bacterial load is), your general toxin load (bacteria, viruses, food toxins, heavy metals, stress, etc.), and how well your body is functioning in general, and specifically how well it's detoxifying itself.
For me herxing has been less black and white than for some - my life is always in constant flux so it's always impossible for me to tell what's a herx. Sorry I can't be of more help!