Just in need of advise

Only you can really know this for sure. Certainly, your judgment may have been clouded by pregnancy hormones and it could still be clouded, postpartum. Not to say that doing what you feel is best for your children is wrong - it's not! But those other factors may have played a part.

So step back. Take a sheet of paper. Draw a vertical line in the center. Label one side Pros, the other, Cons. The question is about staying together.

I can't really tell you what to put down for your personal pros and cons, but consider your children and also your husband's behavior since the affair. Promises are nice, but what else has he done? Gone to counseling? Put this other woman completely on ignore? Taken steps to make sure he never runs into her? Worked with you on your marriage?

As for your children, a big con is the financials in a divorce. There is nothing wrong with considering that. But also consider your own happiness and the lessons you are imparting to your children. Maybe the lesson is to just sit back and take it and let the person you love walk all over you (not a good lesson at all). Or maybe the lesson is to not throw away something important if you're both doing everything you can to fix the problem. Even small children will pick up on tension in a marriage, even if they don't know what's causing it.

Has he given you much detail? or did you not want to know?
Was it just sex, or something deeper?