My fiance and I had unprotected sex between last Monday and saturday every day. My period usually comes the last week of the month, but today (monday) I started bleeding very lightly. I figured I started my period a little sooner, but it lasted less than a day and I'm now spotting a light brown color. Is that weird? Is it too early to tell if it's implantation even though it's only been a few days? Too early to take a pregnancy test?