Help!!

I took a pregnacy test 4 days after the last time I had sex, which was a week ago today, it came up negative. Now today I've starting bleeding like crazy with lift side pain that radiates into my back. I took the tampon out about an hour after I started bleeding and it was full with dark, clotty blood and tissue or skin of some sort on it!! Can anyone give me some help on might be going on with me?? Let me ask this, is it possible to have a miscarriage this early??