my baby is 5 months old. her weight is 5.4 from last 2 months. she has not at all gained weight. what may be the reason. what to do

A. hello dear good evening keep check that you are breastfeeding your baby with the gap of 2 to 3 hours during day and 4 to 5 hours of the gap during night and the babies passing urine 7 to 8 times in a day