idek what the heck is going on

okay so my period is like 2 weeks early. it started yesterday and was supposed to start the 29th. but it's weird because I didn't have the normal cramps, just 3 days of brown discharge. why is it so early? I did have sex February 5th but it was protected & he pulled out and the condom didn't break for sure because I watched him cum. so just wondering why AF is so early?