Cancer may be wrecking my marriage

I am the husband. My wife has been going through the cancer battle for a year now stage 3 curvical. I was holding up well for a while mentally, but have always had depression issues. I had an episode just a few days ago and ended up making a mistake by going onto a married dating website. I completely flaked and anyone that has battled depression where the episodes are very dramatic can tell you that you end up doing things way out of character. I have never been unfaithful and still have not been intimate with anyone other than my wife.

During the past few months my wife did not embrace me at all. She would shy away from me if I tried to get close. I feel terrible. She found out about It a few days after she was going over my internet history, which was actually rather complicated so she must have had a reason or had been doing it periodically anyway.....but now she will not talk to me. I messed up,  but I had a crazy amount of stress trying to take care of my 3 kids and her for the past year. My job had threatened to terminate my position because of all the time I had to be off, me and my spouse hadn't been intimate in over a year, and I had been sleeping on the couch for a year. I am lost because she now wants me out of the house and is telling me I can't see my kids. And the only real thing I needed was to be closer to her in  this really difficult time. Any words of wisdom would be great because I am really struggling mentally, and emotionally as I still very much care for her.