I think reading about (attachment theory) attachment anxiety and attachment avoidance will help you answer this question. A fear of abandonment is central to these two different responses. Impulsivity and affect lability is a direct consequence.

Four core features have to be met for BPD diagnosis: Affective instability; identity problems; insecure attachment/interpersonal difficulties; and impulsivity. Note: Some researchers/doctors group identity problems with interpersonal difficulties.

The present BPD diagnostic criteria is in the process of being revised so that it reflects scientific research. The proposed criteria actually does a better job at explaining this very misunderstood condition. The American Psychiatric Association has admitted the present DSM-IV TR criteria is poorly backed by research. Five is just an arbitrary number.

The 256 possible combinations of BPD manifestation is problematic because people can be diagnosed with BPD who do not meet the four (or three) core features. The proposed criteria eliminates this, because it emphasizes the core traits needed for diagnosis. (I hope this will reduce the misuse of this diagnosis.)

You have mentioned in another thread, you have a hormonal problem. This may explain some of your apparent BPD traits, if it is not being effectively treated.

Questioning a diagnosis is a good thing.