Slow suckle

Meagan
I have a 3 week old and we are finally getting the hang if breastfeeding. My question is when she eats sometimes she sucks real fast, and sometimes downs in milk lol and then sometimes after that she will slow down and suckle a couple times stop suckle a couple times and stop (I let her do this until she pops off) is she still getting milk when she slow suckles?? I only ask because we have a weight check on Monday to see if she is hopefully back to her birth weight, I really want to stick sigh breastfeeding and not be "recommend" switching to formula. Thanks