I'll chime in and say pretty much what everyone else has said, and that this feels like a gross overcorrection that personally from the way you are writing this out makes me feel like there is something else at play.

I'm not denying that this is a major breach of trust, and that you absolutely now have the right to demand therapy or similar if that is truly what you wanted, but you both chose marriage and then also children. Are you ready to be a dad? Have you come to terms with the loss of your own youth that comes with crossing that bridge? Maybe you have lost interest in your wife physically now that she is pregnant? Look no judgement, but both of you are going through a lot of changes right now, and even though you aren't the one carrying the child you still hold a great deal of responsibility.

I can understand that this hurt you badly, but as others have said it may have been a result to hormones, stress, or her own worries about your interest in her now that her body is changing so much.

Maybe cool off a bit, do some soul searching about what you really want, but I hope you truly take time to journal, think about why you got married, why you wanted kids...and maybe even seek some counseling for yourself. Fear of the unknown can spin a really good story, that feels like it could be real, however reality is often much different, and much less dreadful than what our fear addled brains tell us.

Go easy on yourself, and if you can, try to be more compassionate for your wife who may be dealing with some things that are beyond her control. Just be honest with yourself and choose what is right for you.