How do you explain your CTPSD to someone without sounding crazy?

I’d like to explain to a few people in my life why my mood is so irregular and why I have depressive episodes that seemingly come up out of nowhere (emotional flashbacks). I’d like to help them understand that I’m not just having a “sad” or “down” day, but I’m seriously not okay and taking it minute by minute to survive. I don’t want their sympathy, but understanding, so they stop fucking sending me “I’m sorry you’re sad” or bleak, dismissive stuff like that.

Anyone have suggestions on how to approach, without blatantly saying “I was abused as a kid and can’t recover from it”?

Edit in title: CPTSD* 🙄