Hi Ripcurl,
Welcome to bpdfamily
There are probably some things you could have handled differently, if you'd known more about what was going on. I'm not sure it would have made a difference to the outcome of the relationship.
There are a lot of resources here for you to learn more about BPD, why people with BPD act the way they do, and what the non-BPD partner can do to have a better relationship. Even if it's completely over with your ex, those skills will benefit you in any relationship. Those lessons are available here:
Detaching from the Wounds of a Failed BPD Relationship.
How long were you two together, between the second date and the text about "competition"? When did you decide to be exclusive?