Navel piercing

Stephanie
So I had my belly button pierced 3 years ago and it's all healed ect with no infection until I'm on my period then it gets infected and a bit of blood crusts around it, and it's only  appears when I'm on my period. so just wandering if anyone else has this problem and those what it is as piercing shop just says to clean it ect and can't find anything on Google