36 week appointment

I went in for my 36 week apt yesterday at 36 and 1. The doctor decided to check my cervix, and to my surprise she told me I was 3 cm dilalated! This is our second child, but I had no idea the process has begun. Now we need to pack our bags and finish getting everything ready! 😳 what are other mama's experiences as far as how long it took them to progress into actual labor from this point??