My only advice is to give him time and let him lead how this goes. Once you told him it is up to him how he handles this. He may choose to leave. If he stays it is on HIS timeline that you guys will deal with it. You must understand that even though you have had years to know about and deal with this, he’s still in shock. He’s going to be angry, sad, shocked and probably have a ton of questions as to WHY you did this and how you’re going to be able to guarantee it won’t happen again. (All very valid concerns that I hope you’ve worked out in your own head).

THIS is the reason most people DO NOT recommend confessing affairs that have ended if you do not plan to commit adultery again. It is for your own sake that you confess, not his.