my baby is 1month 27days but her weigjt is 3.5only is it fine

A. yes it's fine because babies will lose some weight after birth for a few weeks and after that they will start gaining weight. so assuming that your baby is almost 8 weeks baby may have lost a few weeks and then gained. so try and breastfeed exclusively till completion of six months. that's best for babies. eat well and frequently breastfeed.