Puzzled

I am 29 years old. I have two beautiful amazing daughters.  I am engaged to their father.  We have been together for 7 years.  We have been engaged for four years coming this december.  We have attempted to get married for many times before but never set a date.  The last attempt we ended up trying to we were blessed with the news we were expecting our second daughter. Now I am at the point to be like Is he really the one for me.  I know people might say wow. Two cars, a house and 2 kids later you are questioning this but yes I am....  I only ask myself because for so long he has been not wanting it.  He said to me he does not want to marry me.  Why do i stay?