Hi confusedinlove,
I can see how knowing this will remove that plausible deniability makes this situation even more intimidating.There are a few different strategies that can make this conversation a little easier, and you can find a good rundown of them here:
Be a Blabbermouth! The Whats, Whys and Hows of Talking About Sex With a Partner. In addition to Mo's advice about not doing this in a moment where kissing is already happening, I'd also say that the more you can present it as a low-stakes question, the better. So, saying something like, "hey, I've really been enjoying making out, but I'm realizing I'd be interested in doing other physical stuff as well. How do you feel about that?" And then listen to his answer and use the conversation to talk about what kinds of things you're each okay with.
Too, if it helps to re-frame it for yourself, there's nothing "bitchy" about clarifying boundaries, even if you're doing so because there's something you want to try but aren't sure if it's okay. Talking about boundaries is a show of respect for a partner and for yourself which, to me, is the opposite of bitchy.