George, yes I have known of many affairs happening after somebody has slipped into depression. Some people are sceptical about this, because unfortunately, it is often used as an excuse to explain away the distancing I mentioned earlier - and so a person denying an affair and claiming depression instead, often elicits sympathy and understanding from a spouse. Finding out afterwards that the problem was mainly the affair - and not the depression - can make deceived spouses very angry about what has been called "the depression ruse".
However, you have a clinical diagnosis, yes? I will find an article to post on here that may help you, plus add some words about its author.
I will say this in the hope it will help.
When someone is feeling low and down about other aspects of life; perhaps they have hit a "ceiling" at work and have suffered disappointments there, or they are feeling old/ out of potential/not as attractive as they once were, the arrival of an admirer can have a catastrophic effect.
This person suddenly boosts your ego and tells you you are wonderful, funny, admirable, worthy of respect - and enormously sexually attractive. It becomes intoxicating. If this woman had appeared on the scene when you were feeling full of esteem and energy, she perhaps would have not been able to have the same effect.
I wonder whether when this woman started doing all the above, you were comparing her with your wife's attentions towards you, which like many marriages with DCs, would have been focused on their needs and keeping the family show on the road, with all the organisation that entails? Already, your wife was disadvantaged and on the back foot, just as you would have been if someone had loomed on the horizon for her. I expect by that time, you weren't giving very much to your romantic relationship with your wife at all.
If your wife was trying to keep the family going and dealing with a down, moody husband, I imagine that she wasn't showering you with compliments and affection and was getting nothing much from you. That's perhaps why it felt as though the marriage was running on empty.
I would be astonished if, once you'd become addicted to the OW's attentions, you didn't start to find fault with your wife and behave badly at home. It might help me to understand too, if you answer some questions. Did you think you were compartmentalising the two relationships, or did you find the deceit stressful? Did you find it difficult to have an emotional/sexual connection to more than one woman and consequently, you shut out your wife?
From everything you've said, I think there's a strong likelihood that you will recover 100% of your former feelings for your wife and that they might even get stronger than they ever were, but that is if she is willing to give you a chance. From her point of view, I imagine that her decision is blighted by the utter devastation caused and I'm afraid it makes it significantly worse that you had an affair with someone she has to see in the playground - and who lives in your community. She will feel that she has been made a fool of - and that certainly muddies the waters.
If I were advising her, I would ask her to examine whether she still loves you and would ask her to do the maths. Prior to your affair, were you a loving and supportive husband? Was this an aberration in an otherwise kind and decent man? I would counsel her to insist that you got some solo therapy (delighted incidentally, that you are) and I would tell her that until you had got to the bottom of why you were unfaithful - and had resolved never to be unfaithful again, she should not be declaring that she will try again.
Now that the affair is over, you are seeing the OW with clearer eyes. You are also seeing your wife's qualities again, but you've got a way to go on the latter. You need to see her as a woman with sexual and emotional needs of her own and you need to invest heavily in your romantic partnership.
You need to start giving far more than you will get (for some time) from your romantic relationship with your wife. Her self-esteem will be on the floor right now and what ever you decide to do in the future, you need to build that esteem right back up. Many people in her situation feel erroneously to blame and it is to your credit that you haven't done that.
But for as long as this affair went on (including the pre-affair build up) I'd bet she was feeling very unloved and unattractive - she will have sensed your distance. This will have worsened on discovery. However high her esteem was before, she will be looking inwards, wondering "why she wasn't enough for you."
Added to which, there is so much nonsense peddled about affairs, she will have heard ill-judged comments about her sex-life and that it was somehow her responsibility to prevent you from straying. It isn't logical and it doesn't make sense, but so many people believe that affairs only happen in unhappy marriages, she might be feeling utterly bewildered.
You're going to learn some new things in your therapy, but the biggest lesson for you here is that your infidelity was caused not by your marriage and not by your wife's behaviour - but by your response to your own feelings of low self-esteem. This was all about you and nothing else. The affair partner briefly jolted you out of these low feelings and for a time, you felt alive again and full of vigour and adrenaline. But it was a chemical high and had a terrible side-effect, making your life far worse now than the depression ever threatened to.
I would urge you to reflect on all this and see if any of it resonates. If it does, sit your wife down and the first thing you need to do is to tell her how truly sorry you are - and mean it. Not sorry for getting caught, but sorrow for ever having an affair and treating her so appallingly. Take full and complete responsibility for it too, although you might both acknowledge that the OW's behaviour in all this merits disgust too.
Having said your piece, really listen to your wife and get her to tell you the story of the affair from her perspective. You will wince if she is being honest with you, but you will have to take it on the chin.
I've got lots more I can help you with and I will send you that article, but for now, I want you to think all this through and tell me what you think.
I do think there is hope here - if your wife can start a path to forgiveness and if you work out whether this had not much to do with your marriage or your wife at all.
