My 7 month old son was EBF up until 5 months and now is on BM and solids. Unfortunately, I have to abruptly stop breastfeeding as of today. I am devastated, but beyond that, I have no idea how to shift to formula. I was not expecting this, so I only have about a day's worth of expressed breastmilk stored in the freezer. After 7 months with only breastmilk and limited solids, will an abrupt shift to formula upset his tummy? Should I try to mix formula and breastmilk in increasing increments to get him used to it?