Fiancé has a porn addiction

I said if it happens again I’m leaving and taking our daughter and he swore on us he wouldn’t. The night before last I found out he has and idk what to do. We finally realized that this is his addiction. His dad had this problem as well. I’m stuck and lost and heartbroken and confused. I don’t wanna keep making him excuses. I don’t want to keep falling for the lies. I love him. He’s been my best friend for half my life. But I feel like I can’t just keep saying I’ll leave and never do it. I said if it happened again that was it and here we are, so he choose this. Right??? Has anyone been in my shoes? Please give me advice, I can’t stop crying. I keep telling him how I feel and he cries and is upset but he’s said and done all of that before. I don’t wanna regret not staying with him, but I also don’t want to be that dumb girl who stayed and years from now regret it. What do I do???? It’s an addiction but he continued hiding it. This has been a problem on and off through our almost 5 year relationship, but we’re both just realizing that this is a serious addiction and not just him watching porn. I feel so horrible and like it’s my fault. I feel like I’m not enough and that he wants me to be/look like these girls. I have small boobs and no butt. How can I not feel like he’s just with me because he’s comfortable?? I need help. He agreed to go see a therapist but what do I do for the time being? I lost all my trust in him, how do I just act okay? If I stay how can I ever have sex with him again after making me feel so low of myself. Any help would be great. I appreciate it and sorry for the long post. I’m so lost and hurt and don’t know what to do.

UPDATE : I’m not responding to comments because I want to stay anon. But I guess I have to further explain myself.

I used to not have a problem with porn, BUT when he started to treat me differently that’s when it became a problem. Like making me feel bad about my appearance & not appreciating me. Also the reason why we now know it’s addiction is because how it makes him think/feel. He explained that his mind just says to do it, then until he does that’s all he thinks about. After he’s done watching it, he snaps back to reality and realizes he did it. He was doing it during the middle of the day at work and at his job you’re not even supposed to be on your phones (works at a plant). But he feels he has to so bad he made a way. I know how extra and dramatic it must sound to some, but just know that I wouldn’t be asking for advice/help if I was just being a little brat.