Some suggestions to help you feel more in control:
Go see a lawyer - so you know what your options are. You don't have to do anything but it gives you knowledge, and knowledge is powerful in these situations.
Does she work with the same company? If so, one of them has to go - you can tell their bosses or your wh can quit.
If she is married or with someone, tell them. They deserve to know. Does she know he is married? If not, inform her. You can also tell her family.
Tell everyone and anyone - it shines light on the affair and affairs are like cock roaches, they tend to flee when light shines on them. Plus, it does not allow him the chance to put his own spin on things and make you out to be the bad guy. It also helps hold them accountable.
Pull credit reports, pull your financials (both yours and his). It will show you where he has utilized marital funds to pay for his dates etc. Show the results to him in black and white. I personally made my FWH work OT to pay off his debt he incurred when he had his A.
Go see a doc, get tested for everything. Make him go too. Have HIM admit why you both need testing.
If you are in a state that allows for suing the AP for alienation of affection, do it. Might not net you much, but man it would be so in your face and all legal like.
Tell him you want to GPS his phone, car and you want 100% transparency on all social media, phone, emails etc.
If he cheated during work trips, go with him from now on. OR again, make him quit.
Some men don't want to give up the marriage, so he might be telling the truth there. They compartmentalize the two relationships. Not saying it is right, but it explains how he can say he never intended to leave you. Course, that doesn't mean you can't decide to divorce him.
Show him what he tends to lose if you do divorce - child support/visitation (if you have kids together), alimony - loss of the family home etc. Do it calmly too - that really bugs them.
If he had a car that he did things with her in it, sell it. Basically he has to do the heavy lifting to rebuild your trust in him and the relationship.
lastly, this is just for you too - take care of yourself. Eat healthy, try to get enough sleep, see a doc for medicinal help short term if you need it, exercise and find a hobby - it will help keep your mind occupied. Drink plenty of H20 - and remind yourself, HE is the one that did wrong, you are not in the wrong - you kept your vows. Give yourself time to figure out what you want - it has to be your timetable bc no one else can tell you how to get over the death of your marriage as you knew it. If it turns out you are unable to R with him - you have the info from the lawyer - plus you can always file for D and then stop it at any point. This is now your show...direct it how ya want!
Then lace up your bitch boots and tell him how it is going to be from now on. Don't rug sweep, don't allow him to gas light you - bc whatever he says - triple or quadruple it. expect TT, and expect him to take it undergrown.