Not to sure

My partner and me cannot have sex ATM, due to me being nine months pregnant and baby being really low and my legs and vaginal area hurting to much, but what I let him do is I let him cum on my area and butt, would that enter the vagina to help dilate the cervix at all or would it need to be properly entered....I know it's a dull question and I should know being pregnant but I'm desperate to have this baby, just can't wait any longer now...