Halacha definitely encourages taking care of one’s health. Therefore, your awareness of the need for periodic medical examinations is to be commended.
There is no halachic prohibition to see a gynecologist before being married. Many women decide to go to the gynecologist during their engagement for guidance as to the health implications of this new stage of life. Others go even earlier to develop a professional relationship with a physician so they will have someone to turn to with questions in this area.
Some women (or their parents) are concerned that a pelvic exam or speculum exam could stretch the hymen and change their status as virgins. It is important to know that the halachic status of betulah is based on whether a woman has had sexual relations and not just on the status of the hymen.
In summary, it is important at your age to have a physician who knows your medical history and with whom you can consult and ask questions. If a woman is not sexually active, this could be a family physician or an internist and not just a gynecologist. If you have any menstrual irregularities or persistent abdominal complaints, then we would encourage a visit specifically to a gynecologist. If you go for pelvic exam, indicate that you are a virgin and request that they use the smallest speculum.