Being "too sensitive" is something I absolutely relate with (I also have BPD) and trust me, I suffer everyday. I feel and notice everything way more intensely than regular people, I have chronic nightmares so I can't even rest properly, I really don't think I have had someone in my life that genuinely tried to support me and be compassionate about what it is to have BPD, I also can't afford therapy. So every year even though I learn how to live with this better and prevent it from affecting others, with the self-awareness comes more and more thinking which translates into more sensitivity, more suffering. I understand you profoundly.
This may not be the answer you want to hear but learning to feel it out without letting it consume you is what I would suggest to aim for. Avoiding your feelings and pretending nothing is wrong will fix nothing, be kind to yourself and allow yourself to feel, sit with your thoughts for a bit and then stay active after it (hobbies, homework, time with friends or family, chores). Try to understand where these feelings come from, what triggered you? Why did it hurt you? Self-awareness can help you feel in more control of the situation.
LIke you I have a history of self-harm, what I have realized is that this energy has to be expressed physically, some way or another. When I felt the urge to self-harm I often would make these really violent collages, rip pages off, scribble harshly on the paper, put images that portrayed how I feel and then put it all together. Maybe that can help you too? Art and sports are a great vessel for expression.
Also I like your Pinocchio pfp and username. I hope this serves some help! If you'd like to talk more about BPD feel free to tag me, I think I have quite the experience with it. Cheers and hugs ^^
