ave you had unprotected sex? Sometimes women can bleed slightly around the time of their period if they are preg. but, of course, wont get a full period.
It may also have been implantation bleeding. that usually happens about 7-10 days after conception though.
Check a preg. test if you think you could be preg.
But sometimes a woman can have slight spotting a couple days before their period.
Good luck!