If I could make an educated guess, I'd say that you're looking for intimacy, not sex. There's a huge difference, but girls often realize that the hard way.
Check out what this one gynecologist said: "I've asked hundreds of teenage girls whether or not they liked having sex, and I can count on one hand those who said they did. Once they confront their smashed expectations, many teenagers feel that something is wrong--not with sex itself, but with themselves. So, they try harder to make sex 'work,' to make sex provide those things they think it should: intimacy, love, trust, acceptance, appreciation of their masculinity or femininity, relief from their loneliness. When it doesn't work, millions of teenagers assume something is wrong with them, and turn their anger and hurt inward, resulting in depression. . . . We repeatedly return to certain behaviors such as sex, drugs, or drinking to get something that continually eludes us. When we feel empty, we return to a place in which we hope to find some relief or satisfaction of our desires or needs. Even when our behavior fails to satisfy those needs, we return again and again, trying harder to find what doesn't exist." It becomes a vicious cycle.
You had mentioned spontaneity, and I agree that it is fun to have that in a relationship. The problem is that most people think that they are being "spontaneous" by giving in to their hormones and emotional needs at the drop of a hat. This is often either lust or dependency, under the disguise of romance. But hooking up is very different than pure spontaneity.
For example, while dating Crystalina, I came over to her apartment because she said she needed me to help her with something. When I entered, I noticed that she had scattered rose petals all over the place. She had soft music playing, and strawberries with champagne. Then she took me out to eat at my favorite restaurant, and we had a wonderful time, and I expected none of it. It was spontaneous and chaste--which is something rarely portrayed in the media.
I think that the romantic spontaneity you have in mind is not what a high school guy is capable of giving you. Hooking up may feel romantic and exciting, but it comes at a price, which is the regret when all is said and done. You and I both know you deserve better. So keep your spontaneity--that's a fun quality to have. But in the meantime, don't compromise your purity.
. Meg Meeker, M.D., Epidemic: How Teen Sex Is Killing Our Kids (Washington, D.C.: Lifeline Press, 2002), 78.