What Causes Irregular Periods With Cramping, Clots And Dry Blood?

I 2013. I have not received a depot shot since then. I began having a regular period in December 2013. My periods have become regular (every 28 days faithfully, lasting 5 days.) My last few period were 3/12/2014, 4/09/2014, 5/08/2014, 5/08/2013. This month it seems as though I would ve been scheduled for July 3,2014. To also mention ive been cramping really bad. Instead, on July 5, 2014 I noticed I had a little brown spotting in my underwear. I twisted some tissue, stuck it in my vagina and since faint brown blood. The next morning 07/06/2014 I went to the restroom and my period was bright red and flowing with blood clots. Today 07/08/2014 I woke up with no period, just brown old blood, dried up. So all of a sudden I m cramping really bad and go to the bathroom and here s my period bright red with almond sized clots. I m in serious pain and can t get to the doctor until Thursday.