How do you know if you have bipolar disorder?

I feel like I'm in a manic state. Like extreme euphoria. It could be the coffee I drunk this morning or the date from Saturday, or a little of both, but I just feel so damn happy.

I get like this only when I meet someone new and start liking them hard. But when it goes away I get really depressed like unalive me depressed. That's why I feel like I might have bipolar disorder.

But maybe it's just quite normal to feel this way and I don't have anything. I have been diagnosed with clinical depression in the past so maybe I do have it.
How do you know if you have bipolar disorder?
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