3.5 month old not sleeping!

jade
My baby used to sleep anywhere from 4-6 hours at the beginning of the night then wake approx 2 times for feedings 2 hours apart after that. In the last few weeks it is all over the map. Now she is waking 1 hour to 90 minutes all night long and wants to eat or just fuss a bit. She is teething as well so was recommended to give her Motrin before bed which seemed to help her fussiness but she is still up he same amount feeding or tossing and turning whining a bit. Don't know if it's teething, sleep regression or what?!  She is also usually a poor napper and won't stay down for more than 30 mins at a time. Advice? I'm feeling so exhausted !