Nesting

Ronda 🦄🌈 • Due early April 2016 with my sweet baby girl. My first is now a little boy who was born mid December 2013.
When does nesting start? My last pregnancy I moved 3 times and never could tell the difference between nesting and unpacking. I'm 13 weeks 2 days and just cleaned my entire house because.. I felt like it? Anyone know when it's supposed to kick in?