Eh ada saja yang campur formula dari awal, periode dia balik dalam 2-3 bulan je, normal kok! A few of my mum friends who mix-feed also got theirs back quite early compared to those exclusively breastfeeding, it really depends on how much you're actually nursing versus formula. Kalau breastfeeding banyak-banyak, hormone prolactin tend to suppress menstruation longer, tapi if you're splitting feeds, your body might reset faster. Nothing to worry about, completely normal lah even while breastfeeding!