4 Answers

Stress can be a contributing factor......

Your periods most likely have a "pattern". For example, day 1 and 2 may be fairly "light", but then it kicks in and could be really heavy for a day and a half. Suddenly, it's almost gone, but not quite, and that "trickle" hangs on for 2-3 days. 
Think about how your cycle works.  You'll find a pattern in it.  You can even keep a small notebook where you list the first day and keep short notes about cramps, flow, etc.
Get to know yourself.  

Some months are heavier than others.

If you're concerned, call your doctor.

are you filling up like 3 pads in one hour ? Regardless of that , if you think you're bleeding a lot and maybe have clots, too......go to a GYN doctor.