Baby wakes up a lot at night

My daughter is 12 weeks old and she has been sleeping from 10/11- 3/4 and then sleeps agin till about 8/9 and she’s been doing this since she was like 4-6 weeks old but the last few nights she has been waking up at 1 or 2 and stays awake and then goes back to sleep for an hour and wakes up again at 4 to eat and then goes back to sleep till 6. The one night she woke up at 1,2, and 3 and then at 3 stayed awake for an hour and a half and woke back up at 6:30. It’s just been crazy cause she use to have such a good night routine and idk what’s going on. I want to get her on a schedule but I don’t know how. Someone please help I’m losing my mind.