How quickly can you dilate?

Jen • Pregnant with #2 ❤️ Due June 13
Hi everyone, I'm a first time mom- 38 weeks 5 days due August 31st. I just had the doc check and I'm not dilated at all. I was hopeful because I've been having mild cramping and BH contractions for 2.5 weeks now but they're irregular. How quickly can your body progress to dilate? Is it something that happens overnight or does it take time? I'm thinking my baby girl is gonna be a september baby 😫