UGH!! Help! Missed period and negative hpt.

Okay, I'm frustrated and unsure of what going on.. I had a period last month (July 4th.) I went on for five days (TMI) it was heavy and had clots (again TMI) I was excited and awaiting my period for this month, but nothing came!! I have had cramps, I hat white thick discharge (tmi) I also had clear discharge for a few days and I have tried whatever I could to help my flow happen.. I have taken TWO pregnancy test at home and both day "Not pregnant" I do not want to be pregnant as I have two babies and one I am still breast feeding (think it could be why my period hasn't came..) he will be one in October... I have no idea what's going on and no I am not sure what my cycle is because July was my first period since I have given birth.. I really need some advice on this or whatever input possible. I called my ob/gyn and his nurse told me to start my mini pills and I did on the 14th.. I have yet to have a spotting episode or anything else.. am I the only one or has there been others??