What Causes Missed Period After Taking I-pill Followed By Unprotected Sex?

Hi, i had periods on 10,Jan n after that due to an unprotected sex i took a pill n had periods on 28,Jan again. But after that i had no periods till date only felt water discharge with a little foul smell twice instead of periods. I am also having d symptoms of periods like bodyache n cramping in this time. I am so confused! I am also going through a stress and falling sick often can that b d reason too? Before when ever i had stress i missed my periods. So please suggest me what to do? Thanks in advance.