Time Release Virus?

So, for the past few days, maybe as long as a week but I don't think quite that long, I have been feeling intermittently bad. On a surprisingly regular schedule. Every afternoon around 1 or 2 pm , I feel all prickly and mildly feverish, eyes burning a little, that sort of thing. I thought it was because I had been taking 24-hr Claritin in the morning and maybe it wore off by then, but I didn't take any yesterday or today and still the early afternoon wave of not wellness. It's not bad enough to totally take me out, but it's not pleasant. Mostly, I just don't understand.

And I have two meetings scheduled for tomorrow afternoon, so that'll be fun. Blergh.