what is it??

Every night my LO gets super fussy. I have no idea if she's hungry and wants to cluster feed, or if she's overly tired and can't fall asleep, or if she's gassy and had a tummy ache. It always happens between 5 and 12 at night (yes it really is 7 hours). The only time she's not fussy is when she's on my boob, but she just latches on and doesn't suck. We've tried pacifiers but she spits them out...any ideas??