Probiotic

Started a new probiotic. It's a digestive probiotic by trunature. I asked my GI about it and he said give it a try. My previous experience w probiotics was a failure. When should I start thinking it kicked in? I'm having some cramps and feel I need to have a bm but that's probably coz the effect of both Imodium and Questran wore off. I took them on Monday and as usual I'm constipated now. In the past, I also used to take yogurt fortified w probiotics but this put me into a severe flare up. In addition, I went today down to 3mg of Entocort. Is it correct to start a probiotic and reduce Entocort at the same time or should I have waited?