Wow yeah I so can relate. I haven't had an obsession for a while now. I am also very jealous is the person is close to anyone else. It's so intense! To start with it feels nice but then it's just plain uncomfortable!

It's usually men that I become obsessed with. I never take things any further because I am married but I would take them further whilst single and ended up in a lot of trouble because of it.

Anyway, I understand and it does sound BPD to me.