Very Light Periods

Hello ladies! In May I started working out more often (4-6x/week), I noticed my period is much lighter than usual since then. I have a regular monthly period, never missed one, and the length of days is still the same. But before, I would need to change pads every 3-4 hours bec it would be filled up esp on Day 1. Now, it seems one pad could hold for the entire day (although of course I still change every 4 hours). I want to know if this is normal for avid exercisers? Or is this a sign of overtraining? I hope not..