How to move on

So , hear me out or um ... read me out
My closest friend , well our friendship is one sided , its not even friendship i am just toxic and im obsessed with them , i knew that the time that they’d leave will come , but i didn’t think it’ll be soon , i have borderline, so i try my best not to get attached , i cant handle goodbyes , especially when its someone im attached to , i always tried to not get attached , but something about this person drove me in , and yesterday they left , its been a short while 6 months only , but i feel like im dying , i feel so alone , like something is on top of my chest , i keep panicking , i am so clingy i dont blame them , but when i met them it was my happiest year , now that they left i feel so depressed , my body isnt even functioning well , im having headaches and i keep throwing up , its so weird , never felt this way , it feels like i dont want to let anyone in anymore , they might be reading this actually , im only attached to my older brother and my friend , never been abandoned but this is my first time , im so scared ,