Help pregnant maybe

Rebecca
I'm not really good at tracking my period but I gave this app the beginning and ending of my last period and it said I was supposed to start today but I haven't. And my breast have been super sore and if I run I have to hold them or it hurts really bad. My nipple look darker and bigger... And I still haven't started my period.. I had my son on January 31st 2016. Can someone help me?