Extending sleep? Sleep regression at 3 months?

So my almost 3 month old has sleep regressed 😕. She was doing two 5-6 hour stretches at night since she was 3 or 4 weeks. All of a sudden, she started doing 2-3 hour stretches at night. It all kind of occurred after the time change. It wouldn’t be a big deal for me but I will be going back to work in a week and I was hoping to get as much sleep as I was before because my job is kind of crazy - I’m a teacher of young kids. What happened and what can I do? When she is waking now I’ve been waiting until I know she is not able to soothe herself. I give her a few minutes to chew her hand and attempt to calm. I then nurse her and rock in the rocking chair. I try to put her in her crib drowsy but that can be hard.