Hi docdoc, welcome to the group.
Sounds like you've been through a lot in your 4 month relationship -- it started out "so good" and ended so poorly, so quickly.
It makes so much sense, given the whirlwind pace of your relationship, that you'd be asking
What happened.. !
Have you seen our article on "Surviving a Break-up when Your Partner has Borderline Personality" yet? You can check it out here:
Surviving a Break-up when Your Partner has Borderline Personality
The other resource I thought of when I read your post was our workshop on the phases of a relationship, especially a relationship where one partner may have BPD. It's called "The Difference Between A "Honeymoon Phase" and "Idealization"?" and you can check it out here:
https://bpdfamily.com/message_board/index.php?topic=285168.0Let us know what you think about those resources in view of your question --
what is happening??
and keep us posted on how you're doing.
-kells76