I wish I could give you reasons for your doing this, but I honestly cannot. I think it is key for you to figure out what it is that would allow you to be unfaithful even for a night.

You're allowed to think any way you like but be careful about judging how they handle how they deal with your infidelity, each person is different and keep in mind this is the risk you took when you did what you did. Thing is when you question how they are not talking to them it almost sounds as if you should be given a pass for some reason.

Aside from friends, if you are sincere about all you said, and it does sound like it or you wouldn't be here admitting your guilt in this and asking for advice. dw right now about friends, worry about your relationship, your SO and regaining his trust. You chose this path and no one can do anything to get you back on track but yourself. Thing is, keep whatever he is feeling, you cannot change it directly, if he is feeling betrayed and not trusting you, the only thing you can do is prove yourself once again to him.

You need to go over and above what you would normally do to show him you are transparent and honest with him now. it's going to take overt transparency. don't do things that can even be perceived as hiding anything and if asked for proof, do not be indignant or stubborn but be open and willing to prove yourself time and again, that's what it's going to take. If you really truly love this person you will understand what I'm saying. It's going to be long and hard but if he's worth it, I hope you're willing to go for the long haul