Although borderline personality disorder and bipolar disorder are similar, there are differences. Here are some articles that may help you understand the differences a little bit better:

Disentangling Rapid-Cycling Bipolar From Borderline

How to Understand the Difference Between Borderline and Bipolar

BPD and bipolar disorder, similarities and differences

Bipolar and Borderline Personality Disorder

Note: If you think you have a mental illness, you should always see a professional for a proper diagnosis; do not diagnose yourself, and do not have a friend diagnose you.