Am I having a miscarriage?

I don't know if I was pregnant or not, but I ha almost no period, throwing up all the time, dizzyness and they would just come out of the blue. Then about a week ago I had no symptoms anymore and felt perfectly fine so I stopped worrying about it and didn't even bother getting a test. Today while having sex however I experienced a sharp pain in my stomach and then started bleeding. It's a lot of blood, my period isn't due for two weeks, and it doesn't feel like a period anyway. Also, there are like... I guess clumps would be the best way to describe them, and it looks like peices of skin floating around. I'm worried about what this could mean and my friend said if it is I don't want to know because it'll make it harder on me, but I can handle knowing. So any input would be appreciated.