OP, in my experience friendships are like pretty much everything else in life: self-fulfilling prophecies. It's so unfair, but Viktor Frankel's maxim of "To he who has, more will be given" seems to apply everywhere, in situations big and small.
So I'm guessing that you unconsciously put out the notion that you will be rejected and people unconsciously pick up on this and act accordingly. Can you do cognitive rewiring on yourself? Affirmations and the like? Noticing when the dread sets in and using a rehearsed phrase to remind yourself that you are as likely to have friends as anyone on earth?
Secondly, I think you need to allow yourself more faith and optimism. Notice what's going right - you've made at least one lovely friend - and more will follow. Try not to focus only on the gaps but also on the wins (I say this as one who struggles with this too).
Finally, make yourself vulnerable, again and again and again. Ask if you can join in the second hobby, and the holiday. Do it with a pretend confidence "Oooo I'd love to join, is there a way I can?" and never, ever let your feelings of exclusion or sadness show. Keep it light and confident. And keep trying and asking at every turn, finding the self love and confidence to sound as though you're asking for the first time.
For me the key is to acknowledge how hard this is for you, how sad you are, to yourself in a loving, nurturing way. You need to let yourself know that you are valuable and valued, no matter what happens or doesn't happen with particular friends. You can befriend yourself and, surprisingly, it does help.
Good luck OP. You're not alone - so many of us struggle with this. It's part of the human experience.