why am I so heavy all of a sudden?

I started my period on the 12th it's now the 16th. I change my tampon at least 4 times a day. But I went to the sand dunes this weekend && I was super heavy I only had one clean pants. It went threw the tampon underwear && pants. I've never had that happen before.!!! I just want to know why I'm so heavy I am home now I changed it before I went to bed at around 12:30am, woke up at 11am to find out it went threw my pajamas.! Why am I like this.? I've never had it so bad.