Welcome to SI.
First, there is a book called "How to help your spouse heal from your affair" by Linda McDonald. It's on Amazon or you can even find it for free in PDF form if you search. It's a very quick read, maybe 2-3 hours of reading, but it is considered by many to be the "handbook" of what do in the early stages after d-day, which is where you are now. Start there.
I also recommend checking out the "Healing Library" linked to at the top of these forums. These are articles from the users of this site and are VERY helpful. I suggest you read articles on both the WS and BS pages, to help you better understand both sides of the coin for now.
After a trauma such as infidelity, the BS and the WS both have work to do, and healing to do, however, those two things usually need to be handled independently for a while. It's only been a week. Infidelity isn't something that happened to him last week. It's something he is still going through, right now, this second. He's not healing from trauma, he's experiencing it. There isn't anything you can really do to help HIM right now, because you are still the cause of the trauma. He doesn't know who you are right now. His whole world has been pulled out from under him. Just a week ago, you were lying and hiding things from him, actively betraying him, and now this week you love him and want what's best for him? Whether it's true or not is not relevant. How can HE believe you right now? He can't. Hell, he can't even trust himself right now, because a big part of him is feeling like a fool and a sucker for being fooled and betrayed by his wife and best friend. So the thing to understand is, for now, you can't help him directly. He needs time to process. For most people, it takes 2-5 years to recover. So... what CAN you do to help him?
First and very best tip - make sure you give him nothing but truth. Do NOT try to "spare his feelings", or fall into the trap of thinking, "Knowing that will only hurt him more". The only thing that can hurt him more right are more lies and more betrayals. And if he catches you in a lie or omission (on purpose or not), it will only reset everything back to zero. If you want to start building back trust, then this is where to start.
Next, I suggest creating a timeline of events concerning the affair, and give that to him. Things such as where and how things started, places you went, money you spent, lies told, when there was intimacy (ask him for level of desired detail about these), any letters, photos, texts, etc. This is especially important if the affair lasted more than a one-night-stand. He needs information so that he can try to make sense of what happened, and what he missed. He'll likely have more questions after this.
Be sure to give him all your passwords to social media sites, your phone, PC, whatever was or could be used to conceal affairs. Again, this is to help him gauge what is/was happening. You may have only had one affair, but he doesn't know that. From his point of view, maybe this is simply the one he learned about?
Finally, the very best thing you can do for HIM is to work on YOU. I know that sounds backward, but it's not. The ONLY possible way that he can EVER even consider trusting you again, is for you to really work on how you ever allowed this to happen in the first place, and what steps you take to ensure that it will never, ever, happen again. And that means gaining a real understanding of the "why's" of how this took place, as well as working on real inner change with the result you showing more integrity and loyalty, not only to him, but to yourself. As Ru Paul says, "How the hell can you love someone else if you don't love yourself first?" I'm sure that "a cheater" isn't who you ever wanted to be, right? But here you are. Most people don't cheat because they consider it so disgusting that they would never allow themselves to "go there". Chances are good that, before this happened, you probably felt the same way! But at some point, you allowed it, and with it came all the lies and damage going now. He can't even begin to heal while you are still a danger to him. So the best way to help him, is to become less of a danger to him, and they way to do that, is to work on yourself. Understand?
If you'd like to encourage your husband to heal, that's fine, just understand that YOU can't be his healer for now. His cheerleader? His shoulder to cry on? Sure. His healer? No.
One last thing, which I'll admit is controversial here. Is your husband on this site as well? I ask only because the BS's here can offer a lot of help and support to him, but you need those things as well. Many people suggest that both people being on this site is a conflict of interests and privacy, and it is. That being said, it worked for me. Both my wife and I received help here, and for us, having that exposed honesty helped us both, and also helped the people here to give us better advice, because they could tell what was really going on. It's just worth a thought is all.
Good luck. Keep coming back.