Milk: Yes or No?

Since it's been about six months, we decided to start introducing dairy again.  We started with hard cheese on top of pasta and stuff like that.  We also tried Kefir, a weird yogurt-milk thing, but I didn't really like it.  At a fundraising event, I also had a gluten free cheese pizza.  After multiple experiments, though, we don't know what to think.  After having dairy-loaded cheese pizza, I was perfectly fine.  But, having some shredded cheese one time had me in bed with a migraine.  Yesterday, we tried cheese again, and today I have no reaction.  Now, I think that whenever I have cheese I should write down what I ate and if I have a reaction.  That might help us figure out what is going on.  It's pretty crazy!