How do you know if your hymen is intact?

Examination by a doctor.

Agreed, you will go to a doctor and be examined, Many girls, who have never had sex, has had theirs broken, it is not a sign of being a virgin for sure

As chuck said, having a intact hymen is a strong indicator of virginity (though not anal or oral virginity), while not having a hymen isn't an idicator of not being a virgin. There are countless ways of breaking your hymen without intercourse, and that's assuming that you had one in the first place that was sizable enough to be broken.

In the end, it is your word and not that of a doctor.

Agreed, as Craven said there are a lot of ways for a hymen intact, and its not at all a problem, check with your personal doctor for further clarification