Thread: Why did my period arrive 2 weeks early?

I usually have a normal menstrual cycle that's every 28-29 days. My last period came on the 14th of April and should be due around the 11th to 12th of May. However this morning the 1st of May i have realised it has arrived and it has a light flow and a dark brown colour. I'm also not experiencing any cramps or tummy aches as usual. I had sex 3 days ago but not for the first time, could this be a contributing reason to why my period has arrived 2 weeks early? Also my cycle only changes once a year and it did that already at the beginning of the year.