As someone who had a few contradictory opininions from different doctors, one of which being BPD, it does sound a bit like something similar to what I sometimes experience, both easily getting to obsess over someone and to “forget” and to have to force myself to care later
I would recommend professional help to OP, even tho I am somewhat skeptical of psychiatry myself (in the “its a new science and not rigorously measurable way”). It’s not your friend’s/partner’s/etc. job to fix ya, and I myself ended up wanting to punish people for caring about me, that shit can break ya really suddenly, don’t ignore early signs
Real