What Causes Delay In Menses Cycle?

hi sir i have a question related to delay in periods .my periods was about to happen on july 21st 2014 bt i got delayed for 10 days .then i recommended a gynaecologist..she checked my abdomen and suggested me with some test..like thyroid test ,haemoglobin test bt i had taken the medicine 2 in a day for 5 days...but this is my 3rd day running but still i havenot got my periods...suggest me