I know what you mean about groups doing things without you. My old uni group do things without me, then one day (about 2 months ago) i found out about a catch up and they said ‘oh you should come!!’, and reluctantly (because i didn’t want to intrude) i did. It was great fun and now they invite me more often. Although admittedly i don’t go too often. I used to say no so often which made them just stop asking. There’s only so many times someone can take no as an answer and keep trying.
So I doubt very much they don’t invite you because they don’t want you there, Id guess they simply assume you’re spending time with others now. So give one or some of them a call, a text, or an email. Say ‘hey ___, how’re you going? We should catch up soon!’. I’m sure they’ll invite you then
Seriously you’re great fun, and if you were here you’d be my first pick xxxx