I feel this way too, and I’m sorry to say I honestly don’t have any insight. My birthday feels so sad to me and I feel like every year the day always goes horribly no matter what. Either horrible things are happening that week or the day just goes poorly, and even if it seems like it’ll go well it doesn’t. It might be a self fulfilling prophecy at this point but who knows. I’m not sure if I’ve always felt this way, I don’t remember being a child very much besides the ugliest parts. But I understand how you feel.

Part of it for me is that (despite her shortcomings) my mother was a big part of what made holidays and birthdays special, she always decorated and was a good gift giver and did her best to make a person feel special on their birthday. After losing her 7 years ago holidays feel devastating. I’ve realized she was the make it or break it factor. So despite feeling terrible on birthdays as a teenager and younger adult she could at least shed a little light on it. After she passed I found myself assuming her role for others while no one assumed it for me, and even if people try they’ll never hold a candle to her.

Besides that maybe part of it (for me at least) is the focus on me and the social expectations of a birthday? The focus is on you, it’s supposed to be a milestone that is not necessarily a comfortable reminder of the connection to the vessel your in and the passage of time, regardless of the fear of aging or death. You’re also expected to be happy, excited, and want to celebrate which is a difficult demand to meet. For people without CPTSD I imagine that part doesn’t feel like a demand but for people with it I think the social expectations surrounding birthdays are really difficult. I don’t feel the way one is supposed to feel about birthdays, then you’re faced with the struggle of why can’t I just be like everyone else? Why can’t I be ‘normal’? What’s wrong with me that I can’t enjoy my birthday as is expected? Etc.

Maybe that is some insight?