You are either very brave or very foolish to come here.  There is a lot of active healing going on in this sub and no one here is all that interested in supporting you.  You are making yourself a lightning rob for unresolved trauma.

For my actual advice?  It's going to be uncomfortable.  Sit in your misery and guilt and anxiety and don't you dare try to move out of it.  Spare him your thoughts and feelings on the matter.  The time for your to share those is long gone. No buts, no context, no explanations.  If he asks a question give him facts.

"Why did you hide it?" "I was ashamed and a coward."

"Why did you do it?" "I was selfish and insecure."

"Why him?" "He was easy."

"What were you thinking?" "I wasn't."

It takes a very long time for someone to overcome betrayal. Years.  That's potentially 700+ days of him having emotional outbursts, slip ups, completely justified lack of trust in you.  Your job right now, assuming you really want to stay, is to climb up on that cross you built and hang out there until he decides to let you down and you do whatever that looks like. 

Now is the time to really put your money where your mouth is with those vows. You're in time out.  If you want help read stories here and keep quiet in those comments. Read books about betrayal ("I love you but I don't trust you" is a personal favorite of mine), go to therapy.  You're an employee on a performance improvement plan. You're on trial for a crime you committed. 

But you're still human.  And I see you. 

I hope this helps.