Is it normal that i only feel attracted to my boyfriend now?

Before I met him, I was bisexual and saw the allure in everyone I met. I wouldn't like them all, obviously because personality still factors in, but I could see the sexual potential. Now that I'm with him I'm only attracted to this one person. Looking at other people feels the same as looking at an animal or a small child. They can still be cute, but imagining myself having sex with them makes me want to gag. When I watch porn, it's really just me pretending that the actors are him.

Everybody else I know with a significant other is faithful, but they still have the capability of seeing someone else as attractive. I talked to him and he feels the same way. Is this normal?