However, if you are by chance still contemplating your decision, I can throw out the following (please IGNORE and don't read if your mind is made up).

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This is why we kept asking about what EPs he had put into place to guarantee no contact. As LWFH pointed out to me in my own thread, it is a difficult thing for the wayward to go through withdrawal LOGICALLY and avoid caving in to their urges, because they are thinking EMOTIONALLY (foggy) during this time.
Extraordinary precautions have to be put into place for
life.
My previously wayward H also had contact. I had six months of what we call a false recovery. Many of us here have had it, yet we still went on to begin true recovery. When we spoke with Dr. and Joyce Harley, they both assured me that it was almost "normal" with a wayward who had been so addicted (not acceptable though! and thus the extreme EPs that are necessary), and that if we BOTH wanted to make the (uphill) effort to restore our marriage, it was still possible.
That was why I pointed out to you early on that yes, if it takes following the wayward into the bathroom, then that is what you do.
My H desperately wanted to re-claim his life with me, but it took extraordinary measures to achieve his return to an honest life. Our EPs will have to be in place for life, because his A did not die a natural death, and thus the skank's LB balance with my husband is still positive. Barf, I know, but it is what it is.
The DIFFERENCE that I see though between you and I, is that my H told me the truth once he was nailed to the wall with obvious evidence. It is very telling to me that your H's response was to deny his very own voice on a recording, and then go to immediately delete his Facebook contacts.
Your husband is a serial cheater. The recovery path for a "normal" affair is slim and must be followed exactly to have a hope for recovery. The recovery path for a serial cheater is even slimmer, and so extra EPs have to be in place.
Even if you WEREN'T saying that you wanted divorce, I do think that Dr. Harley would recommend immediate Plan B. With your staying in the family home. With your H still supporting the family. And your refusing to have any more contact with your husband unless he were to meet every one of your requirements for recovery.
Have you had a response yet to the email that you sent to Dr. Harley?