Is it normal to like the sight of blood?

One time when my girlfriend and I were having sex she got her period right as we were finishing. She was really embarrassed but I was strangely fascinated by the sight of the blood. It turned me on, and now I love the thought of having sex while she's on her period but she thinks it's disgusting. It's gotten to the point where I fantasize about it and even find myself getting aroused by any kind of blood, even if it's just from something like a paper cut or on TV. Is this normal?