@Mountaindewed

I had been having a lot of abdominal cramps and related problems and they stopped. It was great! As far as I remember, I just totally quit all at once, and I've never heard anything about needing to do it gradually. Just, if you stop milk and milk products long term, be sure you're getting enough calcium.

You can probably get a lactose tolerance test, which is relatively simple, a lot like a glucose tolerance test, at a doctor's office or they can refer you to a lab. Nobody suggested it for me; they gave me a whole uncomfortable expensive set of barium tests instead! When that didn't show anything, I went to a health food store and bought some lactose, ate a lot, and then AARRRRGHHH! Lactose intolerance all right. I don't suggest doing this.

Good luck finding the source of your problem. I know how yucky digestive issues can be.