Help- Baby suddenly keeps waking up at night!

Hi, my bb is currently 4 months. Previously she can sleep through the night but few days ago she started waking up in the wee hours. Sometimes 3 am, sometimes 4 am, and 5am. She seems to be very tired as she yawns non stop but just can't get back to sleep. Normally we feed her through the night and she is asleep but now because she is awake, when we feed her she cry non stop and feel so uneasy. I read online this might be sleep regression but I am not sure... any tip how to overcome this? Because during the day she will be super tired and restless... end up being so cranky... Thank you...