It's great that you're proud of your bisexuality, but it's unnecessary to tell your male partner or date about it. I know this is a bummer but from my experience it lead to absolutely nothing constructive or good to my relationships.

If you tell him you're bisexual ~because it's pride month or just because and you want everyone to know that about you, even your grand-aunt~ there's one thing that'll come to his mind:

That it's possible that you agree to do threesomes with him and another woman. It's everywhere in porn and in social culture. There's jokes about that. You see that in movies or TV series, or lil allusions to threesomes.

If you say that, it seeds that lil idea. He might not ask about threesomes at first because ~he wants to ReSpEcT you~ but trust me, he'll think about that. He will objectify you based on your orientation. He'll think about the long-nailed lesbians in porn that cater to the male gaze. And he'll imagine you as one of those porn actresses and wonder if a threesome would be amazing with you and another random girl. And then he'll ask you about maybe doing a threesome with your friend Maria, or his coworker Hanna. Not fun and it's impossible to nip that bud.

Declaring your bisexuality to everyone, including your great-aunt Anna, is similar to libfem ideas of "SeXuAL LiBeRaTiOn" and just makes you an sexual object instead of like... a person, a woman. Representation is important but it has to be relevant.

If you're exclusive to him, and that you plan to be with him for the long term, don't tell him the specific details about past partners that are irrelevant to your current relationship. It doesn't matter that you had a short relationship with Alice or that you fucked your common friend Barbara. That just makes it awkward for everyone. Just tell him that you had some partners and that it didn't work at the end. Classy, short and to the point.