Echoing what all have said. If you can see menu ahead make a plan. Ask questions and be direct when ordering - it will get easier and flow on time. I also find that a good server will echo back Cobb salad, vinaigrette, no cheese or other dairy. And when unsure they ask the chef.

I have similar symptoms with dairy as adult onset and prefer not to experience them. They hurt and are not short lived.

It gets easier.

You’ll alway miss cheese though!

In addition to TELLING them about your allergy, you need to ASK them. DOes it have any cheese, does it have any butter, does it have any milk or cream. Its on you to ask the questions.