It's so simple, it should have occurred to me sooner. I react to high sugars. Milk has sugars. Duh. I don't know why I didn't think of it. I really *don't* think I'm lactose intolerant; I don't have strong (or any, really) reactions after consuming dairy, but you know what? At this stage of the game, I'm about to try anything.
I was going to cut myself off cold turkey today since I'm out of milk and it would prohibit me from buying more, but I'm going to start slow. I'm NOT going to buy milk. I'm going to use up a bit what I already have in the house (cheese, cream in coffee, etc). You're supposed to do the challenge for x-amount of days. Some sources say 10, the book I read said 14. I will try 14. So... I will drink no milk at all this week. I will put cream in my coffee (going by my reaction of not having cream in the house this morning for said coffee, I'd say I'm not 'ready' yet), eat up the rest of the cheese I have, but next week I'll be off ALL dairy, and do that for at least a week.
Then I'll re-introduce milk. If I react, I'll try organic milk next. If I react to THAT, then I might have no choice but to go off dairy completely, or in very small amounts. I'll be surprised as to what happens. Stay tuned!
Edit: I'm sensitive to fructose and don't respond well to it, which is why I'm testing lactose. They say the two are usually connected together.