Baby poor apetite

Hi ftm here my baby was 2months and 18 days but i notice she refuse to drink milk and she get fussy.She having a poor apetite and i see her body weight going down but she's totally fine,by the way i am fulltime breastfeeding.Is it normal?or should i worried?#breastmilkBaby #FTM #firsttimemom #pleasehelp #firstbaby #advicepls