The vaginal discharge that you are describing probably has no connection with either the hymen nor a uterine contraction nor bike riding. Vaginal discharge is the most common sign of most kinds of vaginal infections. a vaginal infection can be confirmed with simple a physical examination. A more precise diagnosis of the exact infective agent requires a microbiological examination of a vaginal smear. You can consult your gynecologist to request an examination and the necessary diagnostic smears.