I did something similar, but much worse, and he ended it when he caught me. Having a crush gives you an escape from the problems of your relationship because that person doesn't intimately know you, isn't aware of your faults or flaws, and there is still so much to learn about each other. Things are new and exciting and it's easy to get addicted to the process of getting to know another person.

I don't have much advice, because I'm in a position where I'm still not eating or sleeping, and I haven't forgiven myself for what I did. All I can say is that using a therapist to facilitate self reflection is the best use of your time. You are going to regret it, you are going to be sad, and some days you aren't going to be able to get out of bed.

The most important thing to do now is try to understand why you did what you did so that you never do it again. Problems in the relationship is a cop out- you may have had problems, but you didn't handle them appropriately. You should also probably end things with the colleague and nix the tinder dates for a while. You can't measure your self-worth by women's desire to sleep with you. This is going to be a painful time for you, and you should absolutely lean hard on your friends and family, but don't pull other people, like the woman you are dating now, into pain with you just because you are afraid of being alone. Learning to like yourself again will be highly uncomfortable, but it's supposed to be.