Thank you for your query at DoctorSpring.com
I understand your concern
Delayed periods can be due to many reasons apart from pregnancy. As you have already taken two pregnancy tests you need not worry. I advise you to repeat test two to three days after as results are more accurate after a week's period for the urine pregnancy test.
As stress, anxiety and extreme exercise may be one of the major causes of delayed menstruation I advise you to allow yourself one more week before you consult your Obstetrician.
Hope this was helpful,
Feel free to discuss further,