Sleep regression?

My LO has been such a good sleeper up until recently. She was sleeping 7 hrs at night regularly for weeks. She’s 11 weeks. The past 3 nights she’s woken up at 3 am. It’s strange because she’s not really awake but she’s tossing and turning and fussing a little. She doesn’t appear to be hungry. I finally get her back to sleep around 4 then she wakes at 5am (her usual time) and eats. Has anyone experienced this? How long did it last for you or what did you do to change it? I’m desperate. I go back to work Monday and I cannot make it through the work day or I’m up that much over night!!