Probiotic !

I need to buy a Probiotic but not sure where to get best deal,do you buy monthly count 30 or buy more in bottle to last awhile ?

I use this one. very reasonable, and in general I find Vitamin Shoppe products to be very good.

http://www.vitaminshoppe.com/p/probiotic-chewable-100-chewable-tablets/vs-2600#.VKCznBCM

Do you take the Probiotics to help with constipation?  I am having a hard time with constipation any help would be appreciated.