Is it cheating?

My husband started playing this video game about a year or so ago and he is a very antisocial guy and he used to be an alcoholic. So this is what he does does for fun. He makes friends on this game and one of them is a girl. Ok so what right? It’s just a game.

They talk allll the time along with his other “gamer” friends and she has a bf too. So I’m thinking ok it’s nothing. He helped her with some studying and still I’m like wtf but he would never fucking do something stupid right? Texts and sends pics and memes to his group chat and to his little fun gamer crew and they even send each other christmas presents.....Still innocent right?!

WRONG!!! He just admitted to me two days before Valentines day that for the past year that he and this girl have been flirting and doing inappropriate things over the phone, sending “pics” and god knows what else. And he is only telling me now cause he says this girl is crazy and he told her he wanted to stop months ago but she keeps threatening to hurt herself....and was calling him over and over again.....like WTF!!!

What am I supposed to do? This is cheating right?! I have a right to be pissed. I have a serious reason to possibly want to leave him? I’m so fucking heartbroken. I’m embarrassed. I’m hurt. I feel like I can’t talk about this to anyone because I don’t want anyone to know. I feel disgusted and like a failure and such a loser. 12 years down the drain.