Why should it hurt

I talked to a girlfriend today. I'm going to her daughters baby shower on Sunday. Andwhile we were talking I asked her how her nephews wedding was because I couldn't go. It was February 23 and I had made plans with my girlfriends way back in September to have a stitching day.
They were inviting me and not Ed (the grooms mom has her own issues with Ed) and I couldn't handle being some place where he was. Sitting at the same table with our friends - or they'd have to split the group and some sit here with me and some over there with him. I sent in my regrets and when I did that my friends husband felt guilty and invited Ed.
Now my girlfriend this morning told me he came with a DATE. She said they all sat at the same table and she was on the other side so she didn't really talk to her but said she felt like she was betraying me if she did talk to her. Now, I have no interest in him - so why should it hurt. Honestly - I can't f...ing believe he took a date to something with all our friends. But then he is nothing if not selfish - he actually said to one of them that he couldn't think of the grooms siblings names!! He's known them since they were born and he can't f...ing remember their names.
I guess it just hurts because I'm afraid they are going to forget me and not be my friends any more. There is another wedding in September and I won't go if he is there.