Golly, I've had these fussy, squirmy periods and they're just awful. I completely sympathise.
For me, it was partly about letdown. I got used to taking my son off the "firehose", as we call it around my house, letting it flow into a cloth and then putting him back on.
It was also gas - from the letdown and my oversupply. His stomach STILL drives him nuts sometimes at 15 weeks.
It was also about distraction - he still feeds so much better at night in the dark, with nothing else going on.
And yes, a growth spurt also means fussiness.
What I did was just ride it out. What I mean is, I tried to keep feeds roughly every three hours but if he wanted breast earlier, I gave it to him. If he wanted to feed at night, so be it. The main thing is, I kept thinking, that he's eating enough even if it's at night. That was a "blow the routine" time, where I just tried to keep on track but also, when I couldn't, didn't beat myself up about it.
And truly, it passes. It just passes if you feed through it!