It's hard, so hard, but you just have to go through it, like the bear hunt, you can't go round it, over it or under it, only through it.
My XH was also in another room on the computer, messaging OW. His mobile phone habits totally changed, PIN, wouldn't let it out his sight, slept with it next to him, wouldn't let me touch it whereas before I'd always answered messages for him when he was driving.
My X also refused to attend counselling. I begged him, hoped he would come out of his infatuation with OW, asked him how he could leave 3yo DD. He was so cold and hard, just insisted he no longer loved me so no point in trying counselling.
all my friends and family were astounded that he left and that he could have an affair. It was the last thing I thought he would ever do. But a certain set of circumstances happened and he spent time with OW and that was it, gone.
It's hard, but keep going, eat little and often to keep going, drink plenty of water. Keep yourself busy sorting out your new life. Be prepared for OW to appear. Look after yourself.