Having a miscarriage is very traumatic and a woman can even develop
Ptsd. Then your wife had a second miscarriage.

It’s very possible she is questioning her value and may be suffering from depression. It’s very possible this affair was more an effort to escape and even try to repair her sense of self worth. Your wife should work through this with a therapist. It’s probable she is very emotionally traumatized and confused.

It’s understandable that you are yourself hurt and confused. In fact it would help you to read about how traumatizing a miscarriage can be so you understand the gravity of her challenge. Also it would benefit you to see a therapist yourself.

This should not be a black and white scenario. If you love each other you can get past this challenge.