5 week old fussy at the breast?

So I’m EB and recently I’ve noticed that about halfway through nursing Baby with get super fussy/squirmy at the breast... unlatching and relatching... grunting and tossing head side to side... at first I thought it was a sign of gas or that she needed to burp, so I would burp her and put her back on the same boob.... but she would just get fussy and squirmy again. So then today I tried switching sides. And after I switched sides she was fine! (Since birth we’ve done one side per feeding) what the heck is up with that?