Hi Katie,Forgot one thing for to try, there an exercise called kegels, google kegels for women, I think this will help you with your bed wetting problem.
Good Luck
No, it should cause you to wet the bed. You may have a weak bladder. Have you ever been tested for that? In my opinion, masturbation is'nt a sin. It sounds like it's causing you alot of stress because you think it is though. Humans are sexual creatures. As long as it's not the only thing you think about and you don't do it all day long I think you're just fine and completely normal.
As for a sin, its a thing put out to frighten poor young girls like you, you need to broaden your outlook on masturbating, google dobson and ross, on there you can read a lot more on masturbating, its run by Dr Betty Robson, I think this will broaden your outlook.
Just relax and enjoy.
Good Luck