Well, if your family knows about your two diagnosis’s than I am sure they will understand. It was very nice of your brother to invite you by the way, it’s good to have a brother like that. I agree with everyone here. You are not a dirt bag because you did not go. It would be nice if you would have gone, socializing is very good for us and has many benefits.
Anyway, I don’t want to give you bad advice but in my case, I get invited to do
things with my family and sometimes I don’t want to go because I build it up in my head that it’s going to be some big huge, scary deal. I dread it and I think I can’t do it, but if I force myself to go I often find that it is almost never as bad as I thought it would be and afterward I feel really proud of myself for going, and that makes me feel good. You may be the same way.
Don’t beat yourself up for not going, it’s just one party, you’ll probably have other chances in the future to practice your social skills. If you are on good terms with the girlfriend than I think it would be good to send her a birthday card and wish her a happy birthday and say you’re sorry that you couldn’t attend but you hope she enjoyed her party. A small gift would be good too. It’s just a good thing to do, it’s very friendly and it shows you that you are considerate. It will make her feel good and it will make you feel good too. It’s a very good thing to do.