I have a problem with loose bowels, so should I start taking a probiotic that is supposed to help?

Depends on cause. Constant diarrhea needs to be evaluated. It may be related to a food allergy, inflammation, or infection. First rule out serious disease before self-treating. Also, not all probiotics are alike and taking the right one can make a difference. Look for at least 1 billion colonies and at least several different strains of bacteria.