Is it normal that I masturbate almost 10...

I don't know why, but I am horny all the time.
I am having sex with my wife almost every night, but I still masturbate a lot.
For me, it's a different feeling. I am cumming harder when I am doing it by myself.
My wife is really worried about me but I can't stop. She is also worried that I am not attracted to her anymore, which is not true at all.