Whats the chance theyll keep me ?

i told my husband im hurting in my back real bad and id say in my pelvic area but the dr says my baby is really big and last thursday my dr said if she aint here by this thursday theyll do an ultrasound and see how bid she is and everything so dince she aint here and if she is 2 big do you think theyll keep me cuz im also already dilating some grrr i just want it to be over ....and im 38wks if that helps