[Clare to Henry:] "When I was a teenager I tried to get you to make love to me, and you never would, which of course made me much more determined about it. I think you thought you were going to warp me sexually, somehow." (1.1.33)
Clare explains to Henry that when she met him as a young girl, he took care to act as a father figure instead of as a boyfriend because he wanted to steer away from sexual aspect of their relationship.
[Henry:] […] usually at this point I would be considering how to work my way past various fortresses of clothing, but instead I lean back and stretch out on the sofa. (1.1.101)
In his early twenties, before meeting Clare, Henry was much more of womanizer, interested only in sexual pleasure, not a serious, long-term relationship. But with Clare, he feels different. He wants to take his time and just enjoy getting to know her.
[Clare to Henry:] "I'm sorry! But, you know, in my case, I've been anticipating for years. And it's not like cake… you eat it and it's gone." (1.1.110)
Clare's cake analogy plays to her knowledge that they'll be with each other for a long time, meaning they'll be able to enjoy each other physically for a long time. She knows that this is not a one-night affair, which makes her all the more excited.
[Clare:] As I walk into the kitchen to get a drink someone behind me says, "Check out Miss-Look-But-Don't-Touch!" (1.5.60)
Because Clare is committed to Henry and their secret relationship, and therefore not interested in any of the guys at school, her peers think she's sexually inhibited.
[Helen to Clare:] "You are, like, cross-eyed with lust. I am ashamed of you. How could you let yourself get into such a state? […] Seriously, Clare, why don't you get it over with?" (1.5.60) [Clare:] "I can't."
Clare refuses to have sex with another man just to get it over with. She wants her first time to be with Henry, since she knows that he's the man she loves and will be with in her future. Yet, she struggles with her budding hormones.
[Clare to Henry:] "[…] no, [Jason] didn't rape me. He just – hurt me." […] She peels her shirt off, and I see that her back covered with bruises. (1.5.190)
Jason hurt Clare because she rejected him when he wanted to sleep with her. He saw her rejection as an insult to his manhood and self-confidence, which is why he lashed out and hurt her.
[Clare to Henry:] "But how much sex is enough?" [Henry:] "For me? Oh, God. My idea of the perfect life would be if we stayed in bed all the time." (1.11.24)
Clare seems to be concerned about Henry's strong sex drive. Could his inclination also point to some other underlying personal need?
[Clare:] "And you appeared, and I basically teased you until you couldn't take it. […] And you jumped me and pinned me, and for about thirty seconds we both thought 'This is it.' […] But you got this look on your face and you said, 'No,' and you got up and walked away." [Henry:] "Wow, that's a better man than I." (1.11.42-45)
Henry's love for Clare seems to have helped him transform from a womanizer, out for quick sexual pleasure, to a responsible grown-up man, a man he didn't believed he had in him.
[Henry to Clare:] "I'm not kidding about wanting that much sex. I mean, I realize that it's not practical. But I've been wanting to tell you: I feel so different. I just… feel so connected to you. And I think that holds me here, in the present. Being physically connected the way we are, it's kind of rewiring my brain." (1.11.49)
Henry believes that the cure to his disorder might be sex, in the sense that their physical connection is tangible, something that grounds him in reality.