Hello, I'd like to help you with your question.
What your husband is doing is putting himself first in this situation. He wants to "live out his dream" with this woman and if it doesn't work out, he wants to be able to come back to you. That is, as they say, "having your cake and eating it too". He wins either way and you end up with a husband that thinks of himself first. That is not fair to you.
At this point, your husband has made it clear that he is only concerned with what he feels. He has a choice in how he responds to this woman he is with. He could stop what he is doing and end the relationship to work on your marriage. He suggests he has lost control of himself but in reality, he is just using the situation to get out of it whatever is best for himself and not for you. And he does not need two weeks alone with her to end this relationship and commit to you again. He only needs one short email, text or phone call. But since he is not doing that, you can only assume he is lying to you and wants your permission to cheat on you so he does not need to feel guilty about it.
If you do decide to accept your husband back, he would need to make amends to you. He would need to see what he did
was wrong, work on gaining your trust again and never cheat again. However, if he cannot do those things, the chances he would fall in love again with someone else is very strong. You would never be able to trust in your marriage or get your needs met.
You can try two options in order to deal with this situation. One, you can tell your husband to end the relationship now and force him into a choice. If he still wants you around, he would need to come to counseling with you and be willing to rebuild your marriage. Or two, you can go to counseling on your own and decide from there if you feel the marriage is worth trying to save. Putting yourself first helps you decide what is good for you and not what is good for him.
You can also learn more about infidelity and whether or not it is worth ending your marriage over this situation. Here are some resources to help you:
Surviving Infidelity: Making Decisions, Recovering from the Pain, 3rd Edition by Rona B. Subotnik and Gloria Harris
Transcending Post-infidelity Stress
Disorder (PISD): The Six Stages of Healing by Dennis C. Ortman
Should I stay or should I go? Lundy Bancroft
Either way you choose to go with this, it's important that you do what you can to take care of yourself. You are in pain and the betrayal of infidelity and your husband hurting you like this can feel overwhelming. It's ok to feel sad, angry and even to grieve. Though it is difficult, you need to work through the pain. Be sure to get a lot of support during this time. If you do not have supportive family and friends, talking to a counselor can help you learn ways to cope. And try an on line or in person support group for more support.
I hope this has helped you,