For what it's worth, more anecdotal accounts here, I feel similarly to the way you describe, lasting hours or days, sometimes more or less frequent, mostly in reaction to outer events in my life (the events / triggers behind the mood changes can often be subtle & hard to pinpoint). I do not have bipolar, but I have BPD traits, including the strong and shifting emotions. So when I am happy, I am often ecstatic. My happiness fills the room, bursts my heart, comes with an incredible dose of energy.

You might want to consider keeping a daily mood log. When I did that over a long period, I was able to see just how much my monthly cycle affected my moods.

I can say that I felt something resembling hypomania when I first started an SSRI, and I feel similarly hypomanic when I start a new relationship. This really only felt different in degree to me than my more accustomed happy-energy state. I suspect that the mood issues of BPD & the mood issues of bipolar (particularly the more rapid cycling types) must be very difficult for even trained professionals to disentangle. (I say this as someone whose boyfriend is both bipolar II & borderline. Frankly, I can't tell where one ends and the other begins.)