I think it's hard when you have children also to just walk away, depending on how your husband reacted to how you fond out if he was remorseful about what he did 7 years ago and you love him then I think you both should consider going to marriage counseling to see if things can get better if the marriage counseling doesn't work after about six months then I would reconsider a trial separation and see if you can handle being on your own and possible divorce for the sake of the children you should try every avenue before making such a major decision like divorce. It's hard to get over being hurt that badly when you think that your marriage is okay it turns out that your husband had an affair and produced a child from that indiscretion, you're probably feeling shocked, angery and indescribable pain, you don't know where to turn or how to cut through the confusion and anger to repair the damage. Just because he had an affair doesn't mean your marriage has to be over, if you truly want the marriage to work. You have to beginning to heal and part of that healing is being able to let go, you may want to find out the where, when and why. None of this is going to help your healing. All it does is push you back down to a place that is very hard and painful for you. The truth is, all you really need to understand is why the affair happened, how you can use it to improve your marriage, and how you can keep it from happening again.
Give Yourself Enough Time To Grieve. There's no question that when you first learned about the affair, you were devastated. You begin to question yourself, your desirability, and how you could be so naive. These feelings are horrible to go through day after day, so try to move past them as quickly as you can but if you want to move on examine your feelings and your marriage. Don't feel compelled to "get over it" under the pressure of your husband or children do it on your time and when you are ready to move on. These things take time and healing will actually come quicker if you give yourself permission to process the situation for as long as it takes.
The most important questions that you should be asking your husband is "will you show and convince me that this will never happen again?" and "why did this happen in the first place so we can fix the problem?" He has to gain your trust back and that will take time are you willing to give the marriages some time? You both need to understand why it happened and fix any problems that contributed to it and a marriage counselor can help you to do that and better communicate to each other how you are feeling about what happened. The botXXXXX XXXXXne is that getting over an affair to save the marriage requires that everyone has been heard, understood, and that all needs will be met going forward so that there is no fear that it will happen again and you both need to focus on recreating positive feelings so that the affair isn't always a following, dark, cloud hanging over the marriage.