Hello John,

Some big decisions to be made here and these are points for you to think over...

Do you want your marriage to work? If so, marriage counseling is now a must. Sounds like your wife already has an inkling things are not right as she said she feels she's going to end up being a single mom. That's women's intuition right there.
A good relationship requires honesty and communication and working on. It takes two to tango. Marriage is great if you BOTH want this to work.

Staying in a marriage where you are unhappy, or don't care about it anymore is going to ruin your life, your wife's life and your child's life. Children know when their parents are unhappy.

The obsession with the other woman is probably a symptom of your marriage falling apart or are you really in love with this new lady? Only you can work that one out. I will say though that if you decide to work on your marriage you will probably need to cut all ties off with the woman. That means leaving your job or transferring else where so you have no contact. Remember, honesty is the answer here, honesty to yourself so you don't live with guilt forever.

Decide whether you can live with no regrets on which ever decision you make.

Lastly, always remember that you'll always be a Dad no matter what. That means being in contact with your wife for the next 18 years at least.

Take care.