ive never considered this as a possibility but as a kid i had a very unhealthy obsession with a boy in school that lasted for roughly four years until he eventually left school (i still worry if it was because of me). i would get really angry when anyone else talked to him, i remember when someone got a teacher to swap our places in a class where i sat next to him and i wanted to kill them. i copied everything the boy did, tried to figure out where he lived, would look at rings in a catalogue every day after school and very nearly got my parents to buy me matching rings so i could give him one, im very glad i didnt do that bc i have no idea what i would've done if he rejected it. he was very quiet and whenever i confessed my feelings to him he wouldnt say anything so i took that as him being ok with it. i would follow him around and touch him as much as i could. i realise now that i was basically bullying him, but i was so blinded by my obsession with him i didnt even realise as a kid. the funny thing is i eventually left school as well bc of mental health issues and somehow got put in the same specialised school as him, but by that time i had come out as trans so i have no idea if he knew it was me. he had changed a lot physically but was still very quiet, and anytime he said something to me (which probably happened twice in the whole three years we were in this school) i got sent back to feeling like that obsessed little kid, but it didnt last long thankfully. i have never told anyone about this in my life because im way too ashamed to admit it. its been eating away at me my whole life but nobody knows about it. i feel awful thinking about how my actions affected his mental health. he moved to my school and had no friends when i first met him, and i immediately was obsessed with him up until he left again, i feel so bad.
other than that, in my first relationship, i very quickly became obsessed with my partner, but we were long distance which made it especially hard for me bc i was constantly worried they were cheating on me, even tho they were a really lovely person and they would never do that (i dont think anyway) i was just paranoid. i eventually ruined this relationship with my constant paranoid questions and casually mentioning my suicidal thoughts which really affected their mental health which again i didnt realise at the time. i nearly killed myself multiple times after they broke up with me.
i got diagnosed with bpd last year so i think a lot of my behaviour is because of that. im glad i have that diagnosis now so i can try to recognise my behaviours in the future. i havent been in a relationship for a while because i really worry about how ill behave, and i also have major trust issues so it takes me way too long to warm up to someone and by the time i do theyve found someone else. im not currently obsessed with anyone thankfully. i feel like im going to be single for the rest of my life.