Periods getting shorter and lighter?

Over the past couple years, my periods have shortened from 5 days to 3 days. They have also become considerably lighter. When I first started my period (age 13) until a couple years back (around age 16), I used to have a heavy flow for 1-3 days, and it used to get lighter day 3 to day 5. Since I started using tampons (at age 16) I've noticed my period getting lighter and shorter. I'm 19 now, and my periods last 3 days and they're so light, I can use a regular pad for 24 hours and it won't be full. Should I have reason to worry? I've been regular since the onset of my period, and my flow was just fine until I started using tampons (I've stopped now.)