Huge guilt?

You shouldn't feel guilty about masturbation. It is a completely natural thing to want to explore your own body, and of course once you find out what feels good and makes you climax, the process would want to be repeated. The loss of sensitivity in your oris is not necessarily the vibrators fault, but the repetitiveness probably has a lot to do with it. When we as women do the same thing over and over again our bodies become accustomed to it and it loses it's "spark". Try different things, using different techniques and such. But most of all don't feel guilt about it. It's natural. Have fun, and good luck.