What Causes Bleeding Before Actual Periods?

i started bleeding 2 weeks before my usual periods( a week after having unprotected sex) now, i didn't really understand why.. but my friend insisted that it could be that im pregnant, and that it happens that some girls still bleed even though they are pregnant... so i got used to the thought that I could be pregnant, and that'll I'll take pregnancy test in a week.. and today i got this bloody meaty thing coming outta me.. didn't really hurt. im just wondering what that was.. i spoke to my friend and she again believes iit is a miscarriage.. im just confused and i don't know.. i don't have acess so doctor where i live.. i live so far away in the country