Online affair

I am told it all started so innocently, just chatting on skype, "how amazing is it to talk to someone clear around the world". Then she asked if he had ever had skype sex, he says he said no. The "affair" went on for 6 months, 3+ contacts a week, or more - oh, except when his kids came to visit, but went right back when they left. Why wasn't I important enough not to start in the first place, and certainly why if he would stop for his girls being here, (obviously he knows this is wrong), but went right back for 3 more months.
I'm being told "it wasn't real, it wasn't like we were ever going to meet", then my favorite "I don't know, she just kept contacting me". Took him another 3 weeks after being busted to finally take down his google+ & skype accounts. 5 months after his being caught I am not sure its really over as I found out just yesterday in therapy that he was able to stop the behavior for his kids but not me. Now what.