That's interesting that milk makes you constipated. I was under the impression that people who are lactrose intolerant have bad diarrhea when they consume dairy. Maybe it's not the lactose causing you problems (thus why the pills aren't working). I might suggest fat, but fat actually helps constipation--too little fat makes you constipated. You don't switch fat levels in your milk do you (going from skim to 2% or full fat yogurt to no-fat yogurt and back and forth)?
Pb4 and I have been having a discussion (that has gone off track now, I think) about sugar and its effects. There are some doctors who think that high sugar consumption leads to cramping, bloating and bouts of diarrhea. It is known that the more sugar (and sugar substitutes) that you eat, the more sugar you will crave. I'm afraid it's not an answer to the milk question, but if your sweet tooth is driving you crazy, maybe try giving it less sugar. I've been weaning myself off of sugar for a couple of months now and I really have quit craving it. Sure, I could eat it if I had it (interestingly enough, all mammals save cats--which had no sweet receptors--will eat something sweet even if they're not hungry), but I don't crave it, so I've quit buying it. I'm working now on ridding myself of all food products with added sugar in them (like salad dressing!).