Should I be concerned?

I’ve always had a regular period since I could remember, you know once a month every month for 5 days thing. But just now when I got my days this month, my blood is a lot darker and idk why. Normally it’s been a regular color of red I’d say, now it looks more like a brown color & idk if it’s something I should look into or maybe I’m just psyching myself out. I read that it could be just that my blood has oxidized but again idk this is something that pretty much almost never happens. And this time around I’ve been a bit more nauseous than I normally am when I have my period. :/