What Causes Missed Periods?

Ok last month my period was at the very end of the month and only lasted a few days. Ever since I stopped BC my period hasn't ever been the same. But this month after I had sex (didn't cum in me) a few days later I bled for a couple of days. Well I haven't started my period this month but I have been stressed ALOT and my pee is dark yellow and burns also I am having vaginal discharge with some blood in it. Could all of this cause me to miss a period