This month my period was little bit late and came lighter than usual the first day. There was blood mixed with some brownish substance. Today is my third day and my period should be heavy, but I'm getting almost nothing. I've had unprotected sex before this and I'm not sure if I'm pregnant. Is it possible if I already got my period but it's irregular like this?

Its possible that your having an irregular period but it would be in your best interest to go get a pregnancy test just to calm your mind. I know they say that you miss a period when you get impregnated but taking the test will make you double sure.