As far as i've seen, implantation bleeding is usually more pinkish and you only get little spots. I've had two pregnancies (i'm 35 weeks along in my second now) and i've only seen implantation bleeding once.
Mind you, since I started visiting this forum i've seen all kinds of variations, and my good friend is about 25 weeks along in her second pregnancy- she had an almost normal period at the beginning of both pregnancies- when she was already pregnant I mean- she always seem to have a last period for good measure, even though she's pregnant already.
Did you already get a positive on a pregnancy test? Did you know for sure you were pregnant- or were you just hoping?
As long as you are not bleeding heavily, with clots and stuff, and you are not cramping, then it's absolutely possible that you are still pregnant.
I've got my fingers crossed for you.