I started out drinking commercially made smoothies, and discovered I really liked the taste! To me it's a drinkable yogurt flavor & texture.
I don't believe that what you ate this am was a bad choice, although I am not on any special diet.
The abx might be doing what it is supposed to, it just may be that abx, at that strength gives you diarrhea. It's still very beneficial to start using kefir, as it has many different beneficial bacteria in it, not just acidophilus.
I in no way am connected to or gain anything from suggesting this site, I believe it has the most info & how you can get started by only paying postage, or sometimes for no money, as was the case for me.
Here is the link; Dom's kefir making - users.sa.chariot.net.au/~dna/Makekefir.html