Period smells ???

My boyfriend just told me he thinks he can tell when my period is coming which i thought was normal cos he's learning about me still, it's a pretty new relationship ... but then he says "I don't want to sound weird or anything but every time you're about to get it I smell a certain smell, it's not bad i dont know how to explain it so we'll see if I'm right if you get your period soon" ..... has this happened to anyone ? cos I don't smell anything and i know I don't stink cos I make sure I'm always clean.