What Causes Delay In Period?

I have taken meprate 10mg for 7 days to regularise my menstrual cycle. Doctor asked me to do hormone test and Ultrasound scan on 2nd and 8th day. Since, i got spots on 2nd of taking those pills, i have stopped taking the pills. I did not get my periods. So i have started taking those pills for continuous 7 days. But still didnot get my periods. plz suggest how to proceed now?