It's kind of a long story, and if anyone's interested, I'll go into it, but I had the "invisible bugs" on my skin for two years. I've seen some people on here complaining of similar symptoms on here. After trying everything, I found the culprit: it was the god-knows-what growing in the wax ring/seal underneath my toilet. I replaced it with a rubber seal from Amazon, and the crawlies went away almost right away. Just thought I'd let you all know, it might help some people here.