Okay...
About two days after finishing my period I had sex with my boyfriend, without a condom, and he came in me.. it has only been three weeks since I stopped my period and yet again I just started.. it's not like a typical period, it's more of a deeper red, with extra tissue, and I have recently started slight cramping. Mind you it has only been like ten hours since I started bleeding. However with time passing it's getting worse.
I would assume that I just started my period early but I know my cycle & symptoms..

Another thing, if this were to be a miscarriage could I still take a pregnancy test & get a positive result?

It sounds like you could be miscarrying. Yes you could still get a positive result.

You need to see a doctor NOW!