I feel you. sometimes I also delay an answer or get really axious so I cant sleep.(or cancel spontaneously with a bad conscience) why, if I don't have to I don't go, and if I want to but I am afraid, then with a close friend who knows me. and for Birthday situtation, with friends I normally just invide close or do something small with one or two. family I still can't get along. 
I have not really tips but youre not alone

Even when it’s my birthday I get so anxious for some reason and it’s a bit tiring for me. Like being around more than 5 people that you’re EXPECTED TO SOCIALIZE WITH feels exhausting sometimes😣😪

NUMO ADHDNUMO
ADHD

Is anyone else stressed about making plans with their friends?