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.