2 month breastfeeding

Miya

My 2 month old went from nursing from 15 to 25 minutes to now nursing for 10 to 20 minutes and most times only on 1 breast at a time, when I burp her and switch over she doesn't want to feed anymore but then she will have have her hands in her mouth and lick them. Is this normal?

Went to the pediatrician and she didn't gain any weight on one week but she has pee and poo diapers.