Re: now I'm nervous I killed my supply
Nah, you didn't kill your supply. There are probably a couple of things going on, one or more at the same time.
Could be a growth spurt. Babies sometimes grow in fits and starts, with rapid progress sometimes and slower growth at others. Sometimes those growth spurts can make them want more food than they otherwise might. Your body adjusts but they can get fussy if they aren't getting everything they want all at once.
Could be the night time fussies. Many babies, nursed or not, get fussy at night. There are lots of different reasons, from overtired to overstimulated to gassy to whatever. When they are bottle fed, people automatically assume one of those over nursing, but often nursing mothers automatically assume night time fussies are due to not getting enough, because we can't see just how much they got.
Could be that with your oversupply, he got used to it coming out fast, now that your body is adjusting, he's frustrated that he has to work a bit harder.
FWIW...even knowing all that, I am dealing with a similar issue with my almost 6 week old. He's gaining wonderfully, plenty of wet and dirty dipes. And he's getting fussy at night, doing the same thing, acting hungry, nursing for a bit, then crying and acting like he suddenly can't find the nipple. Cries some more, nurses for a moment, then gets irked off again. And it does momentarily still worry me.
But, I pop a pacifier in his mouth and 9 times out of 10, he stops, which tells me that like yours, he's not a comfort nurser...he wants to suck, but doesn't want anything coming out. If he pops the pacifier out, then I change the diaper, wrap him up and rock him and he's usually out in a few minutes...just tired and ready for bed, not for dinner.