Hi,
I too had a similar experience, it was about 3 years ago. What I learned in the process...
One, the grass is greener where you water it. You would be amazed as to where your marriage can be if you put the effort into it you put into cheating. We often tell ourselves things about our spouses during affairs to justify our choices.
Two, read about limerence. There is a great article from Dr. Frank Pittman called "Romantic Infidelity". It explains the common psychological aspects of an affair, why the emotions become so intense. You simply can't have a healthy love or soul mate relationship with someone who doesn't care about your well being.
Three - the pain I was feeling after the A was compounded by so many things. The reality of it was I was trying to prop myself up with the Ap. I hadn't felt happy for a long time, that was my fault. When you get that barren and numb, you are ripe for acting out. Some people self medicate with alcohol, some with gambling, some people with other people. When you rely on one other person for your feelings, that's an addiction. All the dopamine hits you experience come from one source.
I felt numb to my life too when the affair was over, I couldn't connect my feelings to anything else. It is a painful time. It's just not painful for the reasons you feel like it is. It's painful because you have brainwashed yourselves with all sorts of stories to justify something you knew was wrong. The sooner you can accept that you two were projecting a lot on each other, the sooner you can get better.
I do know the pain is intense, but I also know that looking back the affair was definitely the biggest set of bad decisions I have ever made, and I have paid for that for years, and will continue to do so for years to come. It was not love at all. Love is when we care more about the other person's happiness...when we have an affair we just want the other person to make us happy. Making ourselves happy is our responsibility. Figure out how you can do that.
By the way, I thought the same things you are saying at one point in time, I just needed my fix...I wish I had focused on really fixing myself much earlier because I put myself through a lot of unneeded torment, and I put my H through a lot of unneeded torment.
You can not work with the person that you get your dopamine hits from, that addiction can never be resolved if the source if it is around you at all. You really need to remove yourself from that situation. I am sorry, you are getting this advice because it's truth.
Your AP has shown you she is not in it with you for the long haul. Believe her. Figure out starting today how to move on with some sort of dignity and honor. I would recommend confessing. You will see how much of the fantasy world is dried up when you can see more of the damage you caused while you have been so focused on yourself.
I am not judging you, I have been you. I am telling you what I know as you have asked.