Could I be lactose intolerant?

I recently started drinking rice milk instead of cow milk, and I lost 10 pounds. I changed all the dairy products in my diet out with non-dairy ones. I haven't cut calories, exercised more, or done anything else differently. My stomach has gone down a lot, and I feel better. I'm not overweight, so losing 10 pounds is noticible with me. Could I have been bloated from the dairy?