What's going on?

The last 3 nights my daughter's sleep stretches have completely regressed back shorter and shorter. The first night it was 5 hours, then 4 hours last night, and now tonight it was 3 hours. She has been sleeping 8 hours every night the last two weeks now and I am completely at a loss for what's going on now. She finished leap 3 a few days ago and isn't due for leap 4 yet for another two weeks. She's 13 weeks old. I just keep wondering what on earth is going on for her to now be waking like a newborn again? I'm sure she's going through a growth spurt and used to be a crappy napper but great night sleeper which was fine with me.. But now she's flip flopped to being a shitty night sleeper and a fairly good napper.. Is anyone else having this happen? What could cause a regression like this? I'm completely stumped. Nothing has changed.. She's on the same formula.. We do the same routine each night.. The same routine for naps.. She doesn't have a fever.. Doesn't appear to be sick.. Please tell me this isn't my new normal again. I was so happy she finally got to this point sleeping through the night and I'll literally pull my hair out if she goes back to waking every 3 or 4 hours again.