How much is too much?

Anna
When it comes to the amount that you are bleeding during your period? I have extremely heavy periods and I have to change my tampons so frequently it feels like it gets in to the way of my everyday life when I'm on my period. 
I've heard this can be related to other issues such as endometriosis or pcos.  I am wondering at what point should I be concerned enough to go to a doctor for this?