well this has gotten a little messy. don't know where for you to start first. but you are married so that is a good place to begin. would you and your hubby go to counselling together? with this latest snafu he is feeling pretty distrustful i think. if you decide you want to try to save your marriage then counselling imho is a good way to go. you both need an objective person to help you all work out your relationship.
the next thought is, do you know why you had the affair to begin with? imho his friend was not his friend at all. if he had been he would have said no to you out of respect for your hubby. this whole thing was a double betrayal for your hubby.
i can't sugarcoat this situation cause it's so "polluted". i guess first you need to decide what you wish to do...stay or go...then go/build from there. we all make poor decisions in our life. so you're not the first and i make poor decisions sometimes too. just this is not one of them. i came from a family where mother hurt my dad big time. i swore i'd never act like she did cause it affected my life in a large way and my dad's. i saw the damage done to our family.
i hope you can mend fences if that is what you wish to do.