There's nothing wrong with masturbating, especially masturbating with water, as long as you're not doing it to the point where you turn into a prune.
Periods can be late or missed entirely due to any number of reasons: stress, changes in diet or exercise, illness, or other factors. As long as your sure that you have no pregnancy risk, don't worry about a missed or a late period once in a while. If it's been more than a few months without a period, or if you've got concerns about your health, check in with your doctor.
A douche is a solution, usually of water mixed with some kind of chemical (such as vinegar and water or baking soda and water) that women sometimes use to clean their vagina. We don't recommend douching because the chemicals tend to upset the natural balance of your body's own chemistry, and can actually lead to more infections and problems. As long as you're using water (or very mild soap and water) to clean yourself regularly, you shouldn't have any problems.
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