I feel like I'm sinking

My husband told me that he is unhappy in our marriage. He had thought about divorce and doesn't know where he wants to go from here. He is willing to try counseling. He is not the man I married.

I always said before getting married that if there was any type of abuse or cheating, I'd be done. He is insistent that she is just a friend, that there was never anything physical, thy it's not my worst fears. I honestly don't know what to believe. His actions, as well as hers, aren't showing me that it's just friends. If there was nothing to hide, then why was it a secret? He still has been texting her and has called her. We talked yesterday and I don't think it get us anywhere. I'm glad that he opened up to me cause he should've come to me in the first place. I feel like he's the shell of the man I married. It saddens me beyond words that he seems to have given up. I feel like I don't matter to him. I feel like he has chosen this "friend" over his family. And that's fucked up to me. I have two step children that had to witness their parents divorce. If anything were to happen to hubs and I, they would be devastated. I can't imagine my life without him or divorced from him. That's why I can't leave so easily. I still love him. I still hope that things will turn around and that he realizes all that could be lost. I still want to do anything and everything to fight for my marriage. But how do I do that when the other person doesn't seem to care?
Tomorrow is Christmas. It is Baby L's first Christmas and this is happening. This isn't how I pictured my life. I want someone to shake him and tell him, "do you see what you are doing?!?"
Fuck. This fucking sucks.