It is so confusing, isn't it!?!
The first thing to know about foremilk/hindmilk is that the terms are fictions. Convenient and useful fictions, but fictions nonetheless. You don't make 2 different kinds of milk. You just make milk: relatively watery, high in carbohydrates, and low in fat at the beginning of a feeding, becoming gradually and progressively richer in fat as the feeding progresses and the breast empties out. There's no point at which your breast suddenly turns off the foremilk and turns on the hindmilk.
The so-called foremilk gets a lot of blame for tummy issues and making babies gassy. And it is true that the relatively larger lactose component in the milk that comes out at the beginning of a feeding can result in a baby being gassy. But aside from that there's nothing wrong with foremilk. It contains everything a baby needs, and a baby who eats nothing but foremilk will still grow and develop just fine provided that he eats enough of it. When it comes to infant growth, the QUANTITY of milk is much more important than the QUALITY of milk.
So why am I encouraging you to stay away from pumping/expressing? I mean, your baby is gassy and fussy! Why should I try to talk you out of doing something about that? The reason is that your baby is still so young. During the first 4-6 weeks or so of breastfeeding, the baby is trying to master nursing and your body is using the baby's demand to find the "right" level of milk production. And during the first few weeks, your supply is very responsive to stimulation, so it's easy for a new mom to pump herself into an oversupply problem, which can be a problem which takes weeks or months to fix! When you're having an issue with supply- whether that's too much milk or not enough- it's almost always better to embrace the natural approach (simply nurse the baby on demand) instead of the technological, over-thinking approach (pumps! bottles! technical terms!) which is second nature to modern moms.