Interesting Period

I got my period 3 days early. It came Wednesday morning with a crazy crazy heavy flow. I had to change my pad every 1.5 hours. It came at night I put on a tampon so I can sleep peacefully, and it leaked nonetheless. So before going to work I changed into another tampon, after 5 hours I came home, I was surprised to see my pad clean and it didn't leak. So I removed the tampon, and at night I checked I had some light brown spotting. This morning it's the same. It's very unusual I usually have 4 days of constant heavy bleeding. My IUD is out for 11 months already because I'm TTC. Did anyone have a massive change in their period like that? What can this mean?