BP and BPD can be often misdiagnosed as the other. Or, as some have already pointed out, you can have both. The key to BP (bipolar) is that you have to have had a clear hypomanic and or manic episode. If euphoric, they are easy to spot but if dysphoric or 'mixed' it can look a bit like BPD as you become very agitated, volatile, irritable, inpatient, depressed, impulsive and at times a danger to yourself.

Before 2014 I had gone through many diagnosis's such as Major Depression, PTSD and BPD. At the time I was diagnosed with BPD (2010) I did exhibit almost all the symptoms and felt it fit. However after years of therapy and life circumstances calming down my psychiatrist said to me early 2014 that my BPD had evaporated and he wasn't sure I ever had it, instead blaming trauma on my behaviour.

Then In June/July 2014 I had a mild manic episode which my doctor saw. This convinced him I was bipolar. I then fell into a mixed episode and it was similar to some of the BPD symptoms, they do overlap a bit. I have since been seen to have multiple hypomanic episodes and don't have the interpersonal issues that come with BPD. So either my BPD was cured through therapy or misdiagnosed.

have you looked into symptoms of mixed episodes to see if they fit you. Clinical Psychologists can diagnose. If you don't have a psychiatrist I would recommend you see one.

Good luck.