Is it normal to sleep with him?

I'm a woman to start off, sleeping with one of the men in my college sports team. Anyways, a month ago I slept with him out of the blue. It happened once, thought that was the end of it, but since then I have slept with him more times than I care to admit. We are not really friends as in practices and team events we are strangers to each other. We don't talk unless necessary, but when we are alone its the complete opposite, we can't keep our hands of each other. Neither of us want a relationship with the other, but we can't stop having sex, is this normal?