Only a gynecological exam can tell so go see your gynecologist.

It is not that uncommon for the hymen to erode away or tear "naturally" by the mid teens as a result of participating in sporting activities and/or inserting Tampons and/or natural curiosity and exploring.

EEKs recommendation to see your doctor is sage advice. Brandye, our "resident M.D." urges all women to see a doctor before becoming and when planning to become sexually active.

i agree with them, but something else i learned is that the "cherry" isn't always noticable. My first time, the guy I was with was a bit more experienced and was smart enough to know that for a virgin girl, it can hurt her to enter completely. If the man takes it slowly and doesn't penetrate the girl completely right away, the bleeding will be very little and very possibly unnoticeable.

The other two can correct me if I'm wrong. =]

You're not wrong. Technique and skill do matter and not just for the first time she has sex. I've become far more demanding over time. Youngsters and beginners seem willing to endure a lot more fumbling around than I am.

But some girls never did have a hymen in the first place.
Hymens are variable things.

In addition to having an exam before becoming sexually active, why not become familiar with your own pieces-parts? Grab a hand mirror, flash light or other strong light, and go exploring.

I can pretty much guarantee that a boy knows every square inch of his anatomy, so why shouldn't every girl? Because a hymen can have different shapes and configurations from any of your friends, it is useful to know what yours looks like, how it is constructed, how much of it has eroded away, if any, and so on and on.

You might also find it beneficial to stretch the vaginal opening. One technique is explained in an article in the Index. Regardless of whether or not you use a Tampon, inserting a finger when not aroused and then again when you are very aroused, should give you useful information on how the vagina reacts to stimulation and what it feels like. If you are squeamish about inspecting your private parts, how do you explain being able to let a boy explore you or a doctor examine you?

Make an appointment with the doctor in order to get the much recommended first exam and in the meantime go exploring.