I wouldn't have dedicated five years of my life to my fiance if I knew he didn't want to have children and I feel awful for it.
Do you think your fiance will come to the same conclusion about children?
Nope, he won't change his mind and neither will I.
You shouldn't regret your past five years with your fiance as you have learned a lot about yourself and become emotionally stronger as a result of it. Not everyone wants to have children and it is perfectly acceptable to break up with someone when they don't want to have children and you do. It's a major compatibility issue and something that can't be resolved without one person changing their mind.
How can I know for sure that he doesn't want to have children? We probably will break up soon.
I think he is sure if you brought this up to him already. It's also a bad idea to try to convince someone to be a parent when they don't want to because being a parent takes a lot of time and patience.