Hmom, let me give you a big hug. Then, take a deep breath, and let it out slowly.
First, your marriage is not over until it is really over....as in divorce final. Then it might not be totally over. You don't have to let go, until you want to.
I suggest that you read the Divorce Busting book, immediately. It is a wonderful tool, for YOU. Not your Husband. Do not insist that he read Divorce Busting because you will be giving away all of your tools and tactics.
I am an old timer on this site, long enough to tell you that Puppy's advise is usually correct. My H began to behave much like yours has. He denied and denied an OW. He and our life turned crazy! And a year later I found out it was an OW. He had lied to everyone...and I still have a hard time believing that.
Anyway, after many months of hard work and the support of wonderful people here, we made it. Lots of tears and more than a few crazy nights...but I finally have my best friend back.
I would suggest that you read everything that you can find about MLC and Infideliety on this board. There are many here with very good advice. You have found a bery supportive and save haven.
Most of us are about as happy as we make up our minds to be.