Ang teething ay usually around 6 months pa, pero some babies do start earlier, wala namang problema kung ganyan na si baby mo ngayon! About the poop na may kasamang utot, normal lang yan sa 5-month-olds, especially if exclusive breastfed (meron din siyang looser stools), pero since she's on multiple diaper changes with varying amounts, I'd definitely check with your pedia para ma-rule out kung may tummy upset or lactose sensitivity, one of my mum friends' baby had similar pattern at turned out medyo off lang ang formula mixing niya, so better safe na lang with your doctor!