Had Brown Discharge Week After Sex. Later Had White Discharge. Period Is Late. Pregnancy?

My last period was on January 25th 2013, my period ended thursday January 31st, and on Friday (the first) I had unprotected sex although he didnt finish inside im aware of precum, exactly a week after having sex I had a sort of brown discharge when I wiped but it only lasted for about 3 days, then a week later I had a clear white discharge in a big quantity. I had heard that there were very little chances of pregnancy the day after your period, but my period was due yesterday and nothing. Im very very worried, should I be scared? I thought that the brown discharge could be implantation bleeding , but isnt that supposed to happen when your period is due? Wouldnt it have been too soon back then? Im really scared, please help me