Stringy mucus

LO is 3 months for about a week now I noticed in his diapers that his stools have stringy mucus on them. I’m starting to get concerned I took him to the pediatrician but she said she really can’t give him anything and should maybe try to switch his formula. However he seems to be doing fine on the pro total comfort even though his stools are watery. I really don’t want to switch him but he seems to be drooling and was wondering if maybe that could be the reason why he’s having stringy mucus poop. Is anyone else’s LO having the same issue?