Sleep problems- 3 months old

My baby slept great at around 5 weeks old- she would only wake up 1-2 times per night, but her daytime sleep was terrible and she'd have multiple meltdowns from being overly tired. Since then we have gotten her to nap more during the day, but her night sleep has slowly gotten worse. I returned to work last week and she is now 12.5 weeks old, and close to 15 lbs, breastfed... she is consistently waking up 5 times a night, almost every two hours. I am exhausted. Anyone have any advice? I try ignoring her, giving her a binky, she will only stop by being nursed back to sleep. Plus she has reflux so I have to keep her up right for 20-30 minutes afterwards. 😭