Weird period all of a sudden?

So my period is usually 5-7 days long, I am 21 and it has been this way since about grade 7. All of a sudden since my period in August, my period is only lasting 2-3 days.

I got my period on September 15, and it was heavy as usual. And today, September 16 I don't have to wear a liner or anything. It's just light pink when I wipe.

Is this something I should bring up to my doctor? Or is it not that serious? Last month I thought maybe it was a scare, but the test I bought came back negative, and here we are again. Any ideas?