Sucking for milk: sucking is quite strong, can feel milk flow, baby's swallowing
Sucking for comfort: "fluttering" suckle, no swallowing of milk
Is baby teething? When my boy started teething, he kept wanting to breastfeed too, especially at night.
If teething, try offering cold teether before bed.
Standby teether by bedside. At night, can try using it to soothe baby.