What's going on?

Okay so I wasn't supposed to get my period till the 8th but I got it on Thursday (I never have irregular periods) and my blood has been like almost a brown color and I have been having really bad cramps and I just bled through a super plus tampon in like an hour and a half, and when I took the tampon out a lot of really weird discharge came out and like a blood clot came out. Like what's happening?