I use primadophilus reuteri made by natures way, they sell a pediatric formula and an adult one in the powder form for sure, you must have purchased the pediatric one...I use one tsp of powder mixed with a little water...and no, it's definitely not a waste of money, especially if you get the right one for you.
The reason they market one for children including newborn infants is for those who are not breastfed and able to get the enzymes for balancing out bacteria in the system...I don't know if any other brand markets for infants/kids but it's definitely a good idea.
Also, I would give it more then a couple of weeks it can take a couple of months depending on how much bacteria you presently have to combat.
:)