5cm dialated - no pain?

I’m a FTM, came to hospital this morning at 39w for reduced movements.

They talked about inducing which I would really like to avoid if possible as my hospital won’t allow a water birth if you’re induced.

They offered to do a sweep to try and get me started which I quickly accepted and the midwife was shocked that I was already 4cm - she said the mild sweep has taken me to about 5cm. They’ve kept me up the hospital for now bouncing on a ball to see if we can progress things, I’m getting contractions/tightenings but they’re still just uncomfortable I’m not in any pain (apart from pressure in my vagina/back).

Has anyone else got half way there in terms of dialating without any pain? I’m soo confused, I mean great if things are progressing and I just have a high pain threshold (I’ve never had to experience pain really) but I’m really sceptical?