Hi.. The contractions are going to occur at labour..These contractions increase in frequency and intensity as the labour progress.. Since you have passed the plug and the cervix is dilated, clinically you are in labour.. The duration of labour varies, and can last for more than 24hours in a few people especially during their first pregnancy.. I would suggest that you visit your gynacecologist and reconfirm if the cervix is dilated.. If it has been dilated as you had mentioned, it is better to induce the labour to avoid unnecessary complications.. Speak to your doctor or you may chat with one of the doctors available on this website for further a proper medical advise..