S.H.
3 months old is a growth-spurt time... intake increases and feeding frequency as well.
Next: do you have enough milk production??? If not, baby will not be satisfied and will be hungry... and fuss and not be able to sleep. That happened to at least 3 of my friends.
Babies that age... get tired after about 2 hours of "awake" time. At this age, even a bath is an activity.
Also, over-stimulation can hinder a baby from sleeping.
Or noise.
Over-tiredness... also makes babies/kids not be able to sleep... and it actually can make some be more "hyper" and not be able to sleep, nor to stay asleep.
How do you know she is using you as a pacifier? Maybe she is just hungry.... babies ALSO do what is called "cluster feeding" in which they need to feed even every single hour. They are growing so fast and their intake needs and frequency increases too.... ALWAYS feed on-demand... not by a schedule. AND make sure she is latching on properly and you have enough milk production... otherwise she will NOT be getting adequate intake and she will always be hungry...
all the best,
Susan