CM, I'm so sorry that you've had to join our club here, but you won't find a better community than this one.
First, know that this is not about you in any way. It's not about anything you did or didn't do in your marriage. This whole thing is about your WH's brokenness.
It is very difficult to detach and to "be done". Even when you know it's what you need to do for yourself.
Are you able to get some counseling for yourself?
The Healing Library (see the yellow menu box on the left side of your screen) has great articles to help you through these early stages.
Please go right away and get tested for STDs.
2 kids: DD15 and DS18
Him: The Assclown NPD
OW: "friend" of 15 years
Divorced! Feb. 2010
Everybody, soon or late, sits down to a banquet of consequences.
~Robert Louis Stevenson