Hi, welcome to SI. So sorry you are here, but you will get a great deal of support and guidance and encouragement from members who have walked in your shoes.
I'm glad he cut off all contact, just keep in mind there are other ways to stay in touch, email, social media, burner phones, so stay vigilant and I'd insist he give you passwords to everything. Apparently your husband and this woman have been friends for a long time, so it may be difficult to just cut her out of his life. Just a word of caution
Your husband needs to be an open book, his whereabouts at all times, complete transparency giving you access to everything, and I mean everything.
BTW, is this other woman married?
they slept together 3 times.
^^^Gently, cheaters lie, all of them, they minimize to make it look like it's not that bad. If they've been in this affair for almost a year and are in close proximity to each other, IMO it's been more than 3 times.
I'd insist he write a full timeline of the affair, how, when, where, why. Please don't ever, ever accept blame for his actions, he owns his betrayal lock, stock, and barrel.
In the meantime, be kind to yourself, meet with your MD if you need some temporary medications to help you copy. Lean on TRUSTED friends/family. Lean on us. Get out and get some exercise, stay hydrated, and eat regularly even small meals if you are having difficulty.
There's also another good book, Not Just FRiends, by Shirley Glass. It explains how boundaries get crossed so easily and how to be a safe partner.
You don't have to make any decisions right now, give yourself some time to process all of this, get yourself into individual counseling, your husband needs individual counseling, marriage counseling is a waste of time right now, your marriage isn't broken, he is.