My husband is a sex addict

My husband and I have been married for 10 years, and we have four beautiful daughters. Six days after we got married I caught him chatting with someone in a romance chat room. I still don't know exactly what he was chatting with someone about, but I know it was sexual. About a year later I caught him looking at some sort of porn on the internet. He promised that he'd never do it again. By this point I had a feeling that he was a sex addict, but I didn't know anything about sex addiction. I just let it slide thinking that he would probably look at porn every now and then. Eight years later I found out he was searching for some woman on a Facebook. I looked her up, and she looked like a stripper in her profile picture. I confronted him about that. At first he lied about it, but then he told me that he was curious about her (she was a sakeslady at a car dealership where he test drove a car) so he looked her up. 

He was very apologetic, and again I let it go. Our marriage has been kind of rocky the last several months. I'm so busy with the kids, and he's so busy with his job that we just simply stopped making time for each other. I've been checking his phone because I had a feeling that he was up to something. He's been VERY distant lately. Two weeks ago I found a text on his phone to someone asking what room they were in. I confronted him, and he broke down. He told me that he has a problem, and he can't control it. He has been hiring escorts for sex for the past couple of years. He told me that he has struggled with it since he was a teenager. We've seen a therapist twice since it happened, and he is getting ready to start therapy on his own. I feel for him because I believe him when he says he can't control it. I know he has a real addiction, but I am also extremely hurt by his actions. The last time he had sex with an escort I was pregnant with out fourth child. My heart is crushed, and I'm angry that he put me through this. Had he told me about this years ago I could've left or helped him get better before we started a family. My world is in chaos, but I have to put on a happy face for the kids. I'm having such a hard time and I don't know how to handle it. My husband has had years of practice suppressing his feelings about it. I've had two weeks! This is by far the hardest thing I've ever dealt with.