why am I so hurt?

Va
First off, back story... 5 years ago I was involved in a fling with this guy and we fell hard for each other but he wasn't ready for a relationship due to personal reasons I understood. We haven't spoken in years but I'm friends with him on fb and we share a best friend. I am now married and don't get me wrong, I love him, but what me and this guy had was something out of a fairy tale book. I ruined it with him. Well he's been seeing this girl for a little over a year now and today they announced they're pregnant. I'm beyond hurt. I wish I didn't feel that way cuz I'm happy in my marriage but my heart is sunk and I feel like I can't breathe. I'm so heartbroken. He was never the kids kinda guy and when we were together he told me I was the only one he could see himself having kids with and he wanted to. But I can't. I'm infertile pretty much. I'm happy for him but I wish it was me. I know I sound selfish but I can't tell my husband for obvious reasons. He knows how I feel about this guy. But why am I so crushed? We haven't spoken in years or had any kind of relationship for a very long time. I can't stop my feelings for him. Why does this hurt so much? Ugh.