Grim, being one who doean't have a lactose issue, I actually don't indulge in many lactose based products that often, so I can't say how it would feel. What I would offer is a suggestion of ways to deal with the extreme loss of a regular part of your diet. Take the week to try new things, or foids you haven't indulged in for a while. Instead of yogurt, try applesauce or even jello or fruit cups. Instead of cheese on a sandwich, try a spread you like (hummus or a flavored mayo). I know when I found out I have an allergy to shellfish which occured very late in my teen years ( lips swell and I start having trouble breathing), I took it terribly. But then I started trying non shellfish fish stuff, and I no longer care that I can't eat shrimp or crab. Calamari actually became my favorite seafood item, and it reminds me of a good piece of crab when prepared well.
Great, now I'm fucking hungry.