Okay the last time I had my period was Feb 11.2010 and like last month I thought that I had started and it was light at frist then it was normal well it should have ended by the first of this month and it hasn't not really I'm having a light bleeding when I have my tampon in I don't bleed that much and its brown and when there is no blood I take it out then wipe and I have red blood does anyone know what that could mean.
My periods have never lasted a week they only last 3days and my periods have always been regular. I have been having unprotected sex and before I had my period last month I was 2weeks late with it...
Does anyone know why?

Have you tried a pregnancy test? There are a number of reasons a period may be irregular, but since you are having unprotected sex, pregnancy is very much a possibility. Some women do have some bleeding in early pregnancy.
Try a hpt or see your doctor for a test in the office. They may possibly have you take a blood test, especially if a urine test comes out negative, just to determine whether pregnancy is the reason for the unusual bleeding.
Hope it turns out how you would like it to!