I'm sorry. I think what you said was just fine. Doesn't make it any easier that you have confirmed it and that everyone knows now. But your response was perfect. And that's all you need to say on the matter. Your relationship is your business.
we were the couple that would make it
I hate that line. Nothing in life is certain. Don't let other people's views or beliefs on you or your relationship trouble you. My sister and I were talking this week and she made the statement, "I always thought that you were the perfect one. You never did anything wrong." HA! Right! Let me fill you in on the last 10 years Honey. She saw the Facebook version of my life. She only saw the best parts of me. Didn't mean it was my real life. I just hid the real me, the real issues. They weren't on prominent display for the general public. My sister made an assumption about me and was grossly mistaken.
This will pass Unagie. I promise. Cry, scream, and howl if you need to. Then pick yourself up, brush off the dust, and march on.