Is it normal to have masterbated for 15 years since age 6?

I am a 21 year old woman. I don't know how I developed the habit of masterbation. I never thought it could be harmful or evil in anyway, so just kept enjoying it. I do it almost every day. I started at the age of 6, and was not that regular with it initially. When I came to college, at 18, I started doing it more often. I am not worried about the mental/emotional or psychological effects it could have had on me- because it had none. I do it and forget about it, as if nothing happened.

But what I really want to know is whether it is normal for my biological system to have masterbated for so long? I am a virgin and am scared that this might have some consequences when I do the real thing. Do you suggest I stop now? I have a strong will power and can stop. The reason I continued until now, was that I never even wondered it could be harmful. Recently, however, I have been troubled with thoughts of not being able to be a sensitive partner (for having lost most of my sensitivity through masterbation) when I have sex for real. Can someone please tell me where am I going??