I have pcos.... How do you know for sure when your having a period?

I haven't had a normal period since Dec of 2010. Well I just had a period on may 21st since dec of 2010 but to be honest Im not sure if that was my period or not. I had lots of cramping the period ended up lasting 7 whole days when its normally 5 days but I figured it was because I hadnt had one in so long. Cause I read online that some women that dont have normal periods will sometimes have something like a period because so much blood builds up and their body will eventually just release it. So alot of women mistake that for a period. All I know is it was the heaviest period I have ever had. Basically it was like I just had a baby. How the women can be standing up and its just coming out and it goes all over the floor. So what do yall think?