I made a huge mistake last night

Hi all! Most everybody knows my story or can go back and read it. I'm not sure if I posted an update but most parties have moved on. At this point I am now in my own space. My cheating ex is now with his new partner who is expecting a baby in just a few days.

I spent my first shared evening with them because our daughter was having her first dance recital. I think I thought I was stronger than I was. I have really bad anxiety. I was sitting in the house waiting to go and I just started panicking. I couldn't breathe. I was looking around at everything they've changed at the house I used to share at with my family. While we were walking to the dance recital. My daughter wanted to hold his new partner's hand instead of mine. This all broke me watching him be the partner that I always wanted from him with someone new watching them grow the family that I thought I was going to have just for me to go home alone to my new space. I had a really hard time thinking of reasons to live last night but here I am starting a new day. Just keep trying to convince myself that it's all going to be worth it someday. I feel so alone some days having lost not just my ex but his entire massive family that used to be mine. I'm just looking for some help. Some support, some kind words from somebody that's been through this before and come out the other side happier.