I started with my period on the 23rd of January 2012 and ended on the 29th of January 2012.

Last night out of the blue I started menstruating AGAIN? And it is heavy.

What can cause this?

Get this checked out. Periods can be irregular, coming every three weeks or every five weeks or even longer but this often means that it is not a normal period.

If your under 20 don't worry about it. It happens. My period was regular for 2 years before it got all wack but then straightened up for good.