Baby WAS sleeping through the night

We had a 4 night streak of LO sleeping straight through from 9p - 630a which ended about a week ago and every night since then she's back to getting up once or twice each night. I start work on Monday and was hopeful she'd go back to sttn but that doesn't seem to be the case. I mean, I know she eventually will, but when? Has this happened to anyone else?? I can't figure out why this is happening because literally nothing about her daytime routine, feeding amounts, nap times, etc. has changed. How do I get her back to sttn?! (For reference she will be 12 weeks on Monday. )