The way that he said it makes me believe that he is regretting having the affair and wants to make things right with you but in order to do that he has to find closure with this other woman and make a clean break so that he doesn't get the urge to do it again because he has unresolved feelings for her, what you need to do is talk to him never lose the lines of communication in your marriage just in case there is a chance for a reconciliation between the two of you it's harder because you have a child together. In order for you to move past the affair and start rebuilding your marriage you need to have a full perspective on why the emotional and physical affair took place and what your husband hoped to gain from it. Before this can happen, you have to get herself into a mindset where you will be able to deal emotionally with a discussion about the affair. Talking about it right after learning about it usually means both you and your husband will be emotional but make sure you try to stay calm so that your husband doesn't shut down in the middle of you getting your answers.
There are things you need from your husband before you can forgive him for his indiscretion, first he needs to apologize and feel remorseful although this won't take away your pain it is a beginning to the journey towards rebuilding your marriage. It is important that you communicate to your spouse that you really were hurt by his actions and that you don't want him to repeat the offense in the future, so you need to make sure that he is over this woman. If you and your husband want to know how to save your marriage after an affair, you are going to have to start moving on. In order to save the marriage, you must accept the apology of your spouse and you need to forgive and forget them as well. Trying to save the marriage isn't going to work if you constantly bring up the affair again and again. Accept the fact that it happened, accept the apology, and work hard to go on. The trust is broken when an affair occurs in a marriage, the most important thing is to start rebuilding that trust. Don't expect for trust to be rebuilt overnight. It will take some time. He broke your trust, he has to then work on slowly showing that he can keep his word, he should try to make small promises and keep them. Over time as he continues to keep his promises, trust can be rebuilt, as can your marriage.
Counseling may be another important part of getting the trust back in the marriage and also with a counselor you can find out what made him have the affair int he first place whether it was something that went wrong in the marriage or something he was feeling. He could have went through a midlife crisis also but a counseling can help you both work through the issues in the marriage that made him stray.
I would give it another week and then talk to him about what his plans are so that you can either move on or work towards making the marriage work. Tell him you will not wait any longer than that and if he doesn't make up his mind then you have no choice but to move on with your life, he has to know that you aren't going to sit around and wait for him to make up his mind who he wants to be with. I think he feel sorry for her because she gave up her marriage for him and now has no place to go and that is what is keeping him there but that is not your problem she should not have given up everything for another woman's husband and I'm sorry to say but it just may be karma that this is happening to her now. No good ever comes from being deceitful. That's good that he is in counseling that will help him to work through everything he is feeling. Sit him down and talk to him and ask him what his plans are so that you can make arrangements to get your life back to normal. If he knows you are ready to walk away then he may be pushed to make his decision or lose you.