Jaundice level going up

My baby is exactly a month old and we have been going to polyclinic for weekly check ups. The levels were dropping each visit but this time when we went, the level increased. I’ve been feeding BM in the day and FM at night as recommended by my PD previously. Anyone encountered this before? The level is around 140+ now and polyclinic referred us to KKH to do an ultrasound for his liver. Should I be worried or is this normal?