When is it normal...

To be dilated at 1 cm? I'm only 21 + 4 and I only checked because I've had some painful Braxton hicks and watery discharge. My ob said that Braxton hicks are "uncomfortable" sometimes and cm increases in pregnancy but since the bh kept getting so uncomfortable I just thought I would do a self check to ease my mind. I can't find anything on Google as far as when it's normal to be 1 cm so I thought I'd ask here. The bh still aren't consistent so I don't think it's true labor or anything.