I imagine you would know when you're feeling die off. I've seen people on here say they didn't even feel much until the last week or so.
I would think waiting 90 days between humaworm treatments is best as maintenance, but I imagine an extended course might be needed depending on the severity of the infection, or at the very least doing one sooner then 90 days. If your case isn't quite that bad, then you can take other stuff to help with the problem while giving your body a break from the humaworm. I'm about to get some diatomaceous earth in the mail that I'll be starting in addition to the humaworm, I've heard great things about it on this forum but I can't comment on it's effectiveness until I've tried it. Something to look into and consider.
You say you aren't drinking enough water, you should really start drinking more, it's very important. Don't drink any soda/alcohol or any junk like that.
You say you're taking probiotics, I'm not sure how big of a deal it is, but they state on their website they don't recommend taking them while on humaworm .
Also, one of the things I've been doing along with the humaworm is taking a combination of cayenne pepper,tumeric,cloves, and bromelain powder, sometimes cinnamon. I mix equal amounts and put them into empty pill capsules. I take them throughout the day, especially during meals. You can buy all of those pre-capsulated but it's quite a bit cheaper to do it yourself. Of course it's not like you need to do all of that. Seeing as how humaworm does have cayenne and cloves you could just do tumeric and bromelain, both of which I believe make a nice addition to treating parasites.
I also highly recommend trying coffee enemas. I always thought it seemed pretty silly but I recently decided to break down and try them and I can say they definitely work. The amount of what I think is liver flukes and other unknown parasitic crap that's came out has made it apparent that my liver is probably pretty over taxed right now which I had no idea, and I surely wasn't seeing nearly as much in regular bowel movements, nor in other types of enemas. It produces such good results that I really have to hold myself back from going overboard and doing too many, they're addicting.
Anyway this stuff just takes time, I doubt you'll be completely cured of it with one humaworm treatment. Believe me I know it's gross knowing what's going on in you, but results will come. I'm probably still far off from being cured myself, but I know I'm on the right track.