Hi, and thanks for your query on eHealth forum!
A thin watery discharge all throughout is not a normal feature is generally due to genital herpes. At times the sores are not visible and the only thing that remains abnormal is a watery discharge. It can also be atrophic vaginitis which is common in post menopausal women and in your case heralds a hormonal imbalance. It could also be chlamydial infection or even gonorrhea. Hence it is important to get a complete STD and a complete hormonal panel (estrogen, progesterone, FSH, LH, prolactin, thyroid) done.
It could also be due to infection in the uterus, cervicitis, vaginal infection. An ultrasound via vaginal route or a uteroscope inserted via vaginal route to look at the condition of the cervix, uterus etc, a PAP smear, a vaginal swab test, a culture of the vaginal discharge, a complete STD panel are probably what are required. It could also be an allergic reaction to soaps, cosmetics, douches, razor etc that you use. Since a confirmed diagnosis cannot be given on net please consult your gynecologist to find the cause. Hope this helps. Take care!