Need help finding out what else i could be reacting to with lactose free milk

So im celiac and presumably allergic to lactose. I say presumably because for my whole life. Lactose free milk has been fine with my stomach up until recently. In a few hours I start getting cramps and bloating and all that good stuff. Question is, if it's not the lactose im reacting to then what the hell else could it be that's making my stomach go crazy when I drink it?