The Love Hypothesis by Ali Hazelwood

It was a little embarrassing, the amount of time it took for
her to parse the meaning of it. “Oh. It doesn’t matter. I’m on
birth control. And clean.” She bit into her lip. “But we could
also do . . . other things.”
Adam swallowed, twice, and then nodded. He wasn’t
breathing normally. And Olive doubted he could say no at this
point. That he would even want to. He did put up a good
effort, though. “What if you hate me for this, after? What if we
go back and you change your mind—”
“I won’t. I . . .” She stepped—God, even closer. She
wouldn’t think about after. Couldn’t, didn’t want to. “I’ve
never been surer of anything. Except maybe cell theory.” She
smiled, hoping he’d smile back.
Adam’s mouth remained straight and serious, but it
scarcely mattered: the next time Olive felt his touch it was on
the slope of her hip bone, under the cotton of the T-shirt he’d
given her.