I wish I could help. This feeling is terrible. I also wanted to kill myself months ago, but I feel like getting into TF2 healed me. I don't get panic attacks nor the need to self-harm anymore.
I can't give advices about what to do after breaking up because I never dated anyone ( I don't believe in love & I'm aromantic ). I also don't have borderline personality. The only thing I think could help is gaming. Really, finding a good game does more to your life than you can imagine, at least to me. Online gaming in particular helped me to feel less alone & to build fun moments with strangers around the world. I feel less like an "anomaly" since I started gaming ( though, it's a bit of a struggle if your gear breaks.. ).
In case it doesn't work, you at least know what you have. You could search in some forums what other people in similar situations as yours did to feel better.
I wish you luck.
Gromit
yo, I'm an ordinary guy who accidentally stumbled upon this post, life is fucking shit, no one knows what to expect from it, I'm in a shitty situation myself because of college, I hate everything, but Idk why I want to see tomorrow, do something beautiful by drawing shit in paint. Damn, I'm glad I'm still breathing, if there's a chance to help you, to give you some of my optimism. I'll leave my discord. If you need to talk, I'm ready to listen . my ds is funnymousejpg. It's better to call Saul, you know :)