Hello,
Symptoms of a Vaginal Infection:
Abnormal 
vaginal discharge with an unpleasant odor,
Burning during urination,
Itching around the outside of the vagina,
Discomfort during intercourse.
Womens vagina normally produces clear or slightly cloudy discharge. During the menstrual cycle discharge changes from very  thin or watery discharge to extensive thicker discharge. 
If you have 
brown spotting a couple of days after your period it might be leftover blood from your 
uterus and this is normal.
Symptoms which You have described 
fits to vaginal infecion.
 You can prevent vaginal infection by:
Avoid wearing tight pants,
Limit the use of feminine deodorant,
Change out of wet clothing,
Limit bubble baths and feminine sprays,
Have good hygiene during your period,
Wash after sex.