To me, this song isn't about sex at all, but I can see how it could be about that. Giving everything you have to someone because you think if you do they will love you more or because you're pressured into having it because he said he would leave you if he didn't. But the way I see it, it's about wanting someone that you never even had, missing that person and not being able to tell them because you're so scared of what might happen or what they might think. She needs him in her life and he doesn't even see her anymore than a friend, and he would be fine if she left but if he left her life she wouldn't be able to go on. He can't see her like she sees him because she sees him as a boyfriend, a lover, beautiful, amazing, etc. and he probably just sees her as a friend.
To me, this song isn't about sex at all, but I can see how it could be about that. Giving everything you have to someone because you think if you do they will love you more or because you're pressured into having it because he said he would leave you if he didn't. But the way I see it, it's about wanting someone that you never even had, missing that person and not being able to tell them because you're so scared of what might happen or what they might think. She needs him in her life and he doesn't even see her anymore than a friend, and he would be fine if she left but if he left her life she wouldn't be able to go on. He can't see her like she sees him because she sees him as a boyfriend, a lover, beautiful, amazing, etc. and he probably just sees her as a friend.