I hope you feel better soon. This problem is something that you have been dealing with for a while, and your main problem has been a lack in your self esteem somewhere. The fact that you sought out other women, virtual or not, means that you "needed attention" to help you with your self esteem.

A lot of men "cheat" not because they want to hurt their wives, but more because they have "self esteem" issues and "other women" becomes a way to "get a fix" somehow. This may stretch back to your relationship with your mother where she didn't give you enough attention or approval somehow. You may have even been very hurt by a woman/girl you really liked that shot you down and hurt your ego too. It could have devastated you or tramatized you, so as with many situations of "abuse" or "perceived abuse" a person will often find a need to "revisit" that situation in hopes of a different outcome.

The fact that this problem eventually affected your marriage and you are now being "rejected" is also a "bad result" that can attach to the "old let down you already had".
That in turn is bringing on a way of feeding into a sense of "failure" that you never addressed before. At the same time, the desire for "companionship" will still remain high.

You need to spend time with your therapist to figure out where this problem originated, there is always an origin to it. And that is what needs to be addressed, mourned and resolved. You have to find your way to the point where you can finally make peace with how this all started, to see under the hood of where that ping really started and then finally work it out so you can finally "move on" in a healthier mindset. You need to stop going down the mental path of "self blame" and having the constant thoughts of "unworthiness". You "can" address this issue in healthier ways verses the way you did that hurt your relationship with your wife. Once you learn that you can slowly regroup all the wiser and hopefully develope a healthier relationship again down the road. You can also share what you learn with your children someday, especially when they ask you, "Why" you and your wife broke up, and they will eventually do that. Children always want to know why and will even feel they were not loved enough to keep the family intact. This is also something your "wife" has to learn too. Right now your wife is focused on "her own hurt and anger" so she is not seeing what the children feel. This a a common problem and it is important it doesn't continue to go un-noticed and unaddressed.

Open Eyes