How do you know its a Herx?

For some people herxes are easy to identify.

Some of us (like me) have symptoms that fluctuate during the day...and have typically been worse in the late afternoon/early evening hours. Herxes aren't always obvious to me.

Generally, a herx is a worsening of your current symptoms,and can also be an addition of new symptoms.

If we don't do effective detoxing the herxing can go on for days, or even weeks at a time.

I think that's good that the LLND told you to ease off on the dosages if you herx. If you are feeling worse, then try backing off, and increasing your detoxing...for a day or two...and see if it eases up.
Then you know it was a herx. Taking a few days off here and there will not make much difference - in the big picture - as we are usually treating for many months. You want to be as functional as possible while treating.

Here is a link to good detox methods:

www.tiredoflyme.com/detox-methods.html

So, start off with a couple methods, and every few days, add in another one.
Are you taking a good probiotic? That is very important.

Great minds think alike, Girlie! We were clearly typing at the same time (and I'm a bit slower lol)

The symptom journal is an invaluable tool, especially for those of us with cognitive, memory, and executive function issues. I make entries every day documenting sleep/wakeups during the night, signs and symptoms, pain, activity, etc. and of course tracking bowel movement quality/frequency using the Bristol Scale. Otherwise, doc would ask how I was doing and I'd say, "OK, I guess". Sometimes the most important info is what's NOT happening!

Borrelia&Co is a complex illness and it can be tough to tease out what's symptom progression vs herx, but my assumption is that while actively treating, any symptom's a herx till proven otherwise. I'm the kind who will take the herx, pour on the detox interventions and stay the course, but I did hit a point where progress plateaued and GI symptoms got really harsh, after a year on abx. So we knocked off treatment while my GI tract got back to making solid stools again.

After a couple months, went back on abx and experienced massive herxes, literally on the floor and unable to get up or open my eyes. Like a drunken Irishman, (which I used to be) hanging onto a blade of grass trying to keep from falling off the planet ;-) But right at that 7 week mark, I began to feel it back off a bit.
For me, 6-7 weeks after an abx change is the peak. I've been hospitalized twice and neither time was pretty. But I'm killin'. I visualize a herx as being millions of little spirochetes dying in droves, and I'm grimly happy to be in it. It's tough, but so am I. If I'm herxing hard, I may have to do the IR sauna/Epsom bath routine every day to stay on top of it; I remind myself the little buggers never rest, and so I won't either.

My suggestion is to double down on the sauna. Remember, the skin is the largest eliminatory organ of the body and a 1/2 hour sauna can do the work it takes your kidneys four days to accomplish!