do i leave my partner of 5 years to find someone who i can have a family with?

My partner and i met five years ago-we had both come out of 17 year relationships,and had both been walked out on.We found comfort and became great friends and lovers.Since we have worked hard to get our lives on track and become quite a successful team.She has 3 older daughters 21,20& 18 ,she is 47 and i an 39-when we first started dating i told her how i wanted a family and she said she couldnt have children but we would work out possibilities whe the time came.NOW is the time and she doesnt have any answers(or even try to see my needs)she has her family and thats all that comes first.We do love each other and i dont want to go through the hurt/emotional lonelyness in the hope of a family of my owne that may not happen if i dont find the right partner-but at the same time i dont want to die alone wishing i should of had experienced being a father and bring up a family.
Not a easy answer i know but any help we be most welcome! Thanks