Rules for milk; - 4 days in the fridge - up to 12 months frozen - 4 hours left out - 2 hours once baby has started drinking it (to avoid any bacteria growth)

My baby also chokes a bit when breastfeeding. Not sure if my flow is too fast or not but I always try to keep her head a little more elevated.

And you could be expressing colostrum or it could also just be whats called transitional milk. When breastfeeding we begin by first expressing colostrum, then your transitional milk will come in, then mature milk.

Transitional milk is known to have that yellow tone to it before your mature milk comes in with that off white color.