Mood dropped like a sack of potatoes and hit me like a ton of bricks

When going home an hour ago, after celebrating oldest sis' bday (and her boyfriends dads bday aswell) my mood suddenly dropped like crazy.

I think it's because my 40th bday is in just over 6 months, and mom keeps insisting on celebrating that day. I haven't celebrated my bday since my early teens.
Something about "everyone" suddenly caring and wishing me a happy bday makes me feel especially lonely. Probably bc I hardly ever talk to most of them the rest of the year, so it feels fake.

Also, mom makes everything about her no matter the occasion, so she takes it personally when I tell her I don't want to celebrate.
I'm her first born, so my bday is her day of celebrating being a mom, and she loves attention. I hate being the center of the attention. But bc it's technically my day she insists on grabbing attention by using me as an example of how great a mom she is and yada yada yada. She's not a good mom at all, however, which makes it even more awkward.

Anyway, I'm already dreading my bday this year bc of her.
All I wanna do is stay at home with Pantera (my cat, not the band) like I do most days.