Every year I feel a deep sadness leading up to my birthday and I don’t know why. Can anyone else relate?

My birthday is at the end of this month and something I’ve noticed is that every year leading up to it (from a few days to even a whole month before), I start to feel pretty miserable if I’m being honest. And I have no clue why that is. I had birthday parties growing up and now I usually go to dinner with some of my family (not because I want to, it’s because I know they’d be disappointed if I said I didn’t want to do anything). I receive gifts, get told “happy birthday”, etc. Also, I’m not scared or upset about aging. Basically, I can’t think of any specific event or reason that explains why I feel so down. I can handle these feelings and allow them to come and go, but I wish I knew why they’re here in the first place because at least then maybe I could do something to mitigate them. Idk. I guess I’m just looking to see if anyone can relate, get some perspective, stuff like that. Thanks.