Hi Kathy, I'm so sorry for your situation, but glad you have found the forum. You'll get some wise advice here. There are many people who have experienced just what you are going through and will help.
One of the first things you should do is buy the book. I preferred DR as it is more up to date and has specific chapter on infidelity. Also, be careful to keep DBing close to yur chest, and be cautious about browsing histories and so on if you are living together.
Be aware that your H probably wants to continue the A without there being implications within the family home. He will likely want to stay in the marital bed whilst carrying on the A. I moved out the day my H disclosed the A. Our sitch was different in that I have a SS, but we have no kids together. Most people advocate not moving out - either out of the MB, or out of the house.
I think you probably need to accept that your H will be in contact with his AP for some time. A's are notoriously addictive, and even though part of him may want to work on the M, he will probably keep getting drawn back into the A - because it makes him feel GREAT just now. But most A's fizzle out between 6 months and 2 years. Why? Because they are based on fantasy, built on deceit and have no solid foundations to sustain the R when reality creeps in. Only 1-3% of A's lead to marriage, and there's a 75% D rate for those who do marry. Dismal stats if you are having an A.
IMHO, the important things right now for you are boundaries and protection. If you don't want your H in the marital bed, have a look at RAI's thread in Newcomers. There is a helpful post from Wonka on stating that boundary. There may be other boundaries to think about. Others have found 'artifacts' from the A in their homes and have told their S's they won't tolerate and if they find any such things again they will dispose of them, and so on.
Wonka has a boundaries cheat sheet in Newcomers, and you may want to have a look at that. You'll be on moderation initially, so replies may feel slow. But stick with it and keep posting little and often.
Also, be aware that your actions are very unlikely to snap him back into reality. Google affair fog for more information on that. You are likely in store for a bumpy ride, which may take many months, or even years. The best thing to work towards is greater detachment from your H, and keeping the focus on you and your kids. The more you can do for yourself and look after yourself the better.
My final thought is - given your ages - similar to me and my H, there may be an element of mid life crisis in your sitch. I would caution about labelling your H as in MLC - but it has helped me to be aware of what can happen in MLCs. It certainly takes some of the sting out of some of the things my H has done.
Keep posting, and take care xx
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus