probiotic drops for tummy pain?

Sonia
My baby is 6 weeks on enfamil gentlease, she eats well and wets her diapers a lot, but everytime she poops she screams like she is in pain... is anybody going thru the same thing? The doctor told me to try mother bliss probiotic drops.. its been 3 days now and I don't see a difference.. any suggestions?