This is a tough one, I have been there with my ex. We had been together 8 years when he went of and got another woman pregnant.
Difference is we had 4 children together and he had another two from a previous relationship. I had no issue with th older two. Because I had made the choice in the beginning.
But I really struggled with his infidelity and it leading to this child.
He told the woman he wasn't interested, and didn't want to know.
Thing is I never could stomach being intimate with him after that so....after another 2 years of trying to fix it we went out sesperate ways.

All the best for you and your future though.