Period and pregnancy help?

I posted a question yesterday about how many days after unprotected was ok to take a pregnancy test. my periods were due any time now and this morning I got some brown discharge which I usually get when I start a period but now it's gone, like I've had no more and there's nothing when I go to the toilet. There was only a small amount to begin with. I keep getting twinges which I usually get before my period, so is there a chance I could be pregnant?