What Can Cause Fainting?

I did not leave my tampon in for more than 7 hours, but after i took it out i went into the shower, and then i started blacking out. Thankfully, I got out of the shower before I fainted i told my dad i was about to faint, and he put ice on me and stuff. Its been an hour since and now I have a head ache and i do not feel comfortable telling my parents about how this incident may have something to do with tampon use.