Kristen,

<< When I tried to re-introduce them
 into my diet, I got severe reactions (cramps, diarrhea, gas).  Now I
 cannot tolerate any milk products.

Sounds like lactose intolerance to me. You can find out for sure by going to
a gastroenterologist. Lactaid doesn't always work in real life experience. I
have IBS too but the lactose symptoms are different. I use Citrucel  for IBS
and that works pretty well. Milk is hidden in lots of products so you could
be ingesting it without realizing it. Check labels for whey and casein too.
Good luck,

Diane K.