Hello @Flossy92 and welcome to the forums.
I'm sorry to hear that you struggle with depression, PTSD & BPD. I also have depression & PTSD, so I can understand how you feel to a certain extent.
That saddens me to hear that you feel like others don't listen and take you seriously, because you're trying to seek support and I commend you for that, it can be very hard to do. So well done for continuing to try.
I guess it's common for people with mental illnesses to feel that way, at least in my experience anyway, I feel the same way you do very very often. But I want to assure you, I, aswell as others here, will listen, and take you seriously.
It's not "all in your head", as you quoted, it's something you unfortunately deal with. Sadly, lots of people don't understand, but we on the forums do. I hope you can find some support and connect with users here, because I promise you, we will listen, care and support you, and take you seriously.
You're worthy, cared for and loved, so please don't feel like you don't want to be here. I know that's much easier said than done because I feel the same a lot, but the world is better with you in it, even if we may not know each other, I still agree with that.
Please take care of yourself, I'm here if you want to talk, but please don't feel pressured to respond, I just wanted to welcome you and say that I care, as do many others.
Lots of love and hugs to you, and please be safe.