Regarding sexuality, if there's anything Doctor Sue on the Sunday Night Sex Show and all her psychiatric compatriots say, it's, "There's no such thing as normal."
Do you hurt yourself doing this? Doesn't sound like it. Is anybody else harmed? I couldn't see how. What is the result? A good climax. How is this, in substance, any different from masturbation?
Just wash your hands when you're done, PV, and make sure all the mascara is out of the sink. Enjoy yourself. Life is too short not to.