What to do if baby is fussing at the breast
Babies can fuss at the breast for a number of reasons. I copied this list from KellyMom as an example:
Does baby need to burp?
Baby wants a faster milk flow
Baby is done nursing for the moment
Baby prefers one side
Fussy in the evening
Low milk supply
For us, aside from growth or developmental spurts, reflux was an issue. After we solved it, we had easier nursing. It got a lot better after three months, too, after the evening-fussies went away.