Hi mommy Mishy!
There could be a lot of factors why a baby is fussy in the breast so as a caring mom we should take note of everything that may cause the discomfort.
As an exclusively breastfeeding mom myself, I check if my little one is not feeling too hot, living in the Philippines (and no airconditioning) I ready some clean damp lampin beside me and wipe it to my little one to ease her. So far it worked for me.