Welcome to SI and I'm sorry that you're here. The Healing Library contains a list of the abbreviations we use, and is a great resource. There are some pinned posts at the top of the forum that are very helpful, too. The ICR (I Can Relate) forum has threads for various scenarios, like if there is an OC (Other Child), etc.
Cheaters lie, and then they lie some more. Your WH (wayward husband) broke your trust and it takes a lot of consistently trustworthy behavior over time to get your trust back, and then it is never at 100%.
It's ok to take your time to decide what you want, whether it's R (reconciliation) or D (divorce). We're here to help you get out of infidelity.
If your WH is truly wanting to R, then I suggest getting a copy of How to Help Your Spouse Heal After Your Affair by Linda MacDonald. (I guess there are 2 books with the same title, so be sure to get the MacDonald book.) For R to work, both partners have to be all in. Unfortunately, it is tough work.
IC (individual counseling) for both of you. If you can find a betrayal trauma specialist, it is very helpful. He needs IC as well to identify his whys. MC (marriage counseling) can come later, after you've individually healed. Unless you get a stellar MC, they can help with blameshifting - putting some of the blame for the A (affair) on you.
The A was his choice. Nothing you did or didn't do, said or didn't say caused him to cheat. He did it because he had motive and opportunity. WSs are pretty good at re-writing history to make others the bad guy and they are the victim.
Also, if there was any physical aspect, you both will need to get tested for STDs. If you're struggling with depression or sleep, ask your doctor for meds to help you through this.
Healing from infidelity takes years, so it's a marathon and not a sprint.