Personality disorders aren't caused by taking a med. They are long-standing patterns of behavior that are pervasive through your whole life, with roots that go back to childhood and adolescence. But it is true that BPD and bipolar can resemble each other, and there are plenty of people who have both.

Also, by definition, if your only manic episode was triggered by medication, you can't technically be diagnosed bipolar. The criteria for bipolar disorder say that it is not induced by any substance. But what you experienced does sound like a manic (or mixed) episode. It is important to be aware that anti-depressants can have that effect on you. But I wouldn't call you bipolar if you don't get manic when you're not on antidepressants. Even if your doctor decides to use a mood stabalizer instead.

You and I have had so many similar experiences! I also had at least one (maybe a couple more) manic or hypomanic episodes when I started to take St.John's Wort. I hadn't ever not been depressed before discovering SJW, and I overdid it a bit at first. That only happened the first few months that I took SJW. There have been a few times after that when I tried to get manic and took too much SJW, and I don't seem to be able to get manic on it anymore. So you might be fine on antidepressants.