My wife cheated on me.

My wife had an affair 4 years ago but told me 3 months ago.  She had sex with a co-worker in a hotel room on a work conference. She was tipsy and felt unhappy in our marriage. She went back to his room as they did with all there work friends but in this case they were alone. She said he made the first move and did not expect something to happen. She kept this secret for 4 years from me. She was scared of losing me and was ashamed of herself. I feel the last 4 years have been a lie. I do take blame to her feelings as during the years in big arguments I tended to bring up the divorce word or insinuate that things are not working instead of comunicating as adults. I was stupid. This made her feel very unsafe and unloved in our marriage. Yeas of hearing the divorce word will take its tole on a marriage. Well, she felt weak and made a mistake. She said she regretted it as soon as she did it and left the room and didn't sleep over in the hotel room. We are seeking help but what do I do now? It hurts like hell.