Hi thanks for your question.
Your periods are over due by more than 12 weeks and your 5 pregnancy
tests are negative.
There is a long list of causes of delayed periods other than pregnancy and tension is commonest cause for delayed periods.I would suggest you to consult a gynaecologist who will be able to evaluate you for cause of delayed periods. You may need ultra sound
abdomen along with many more investigation to determine cause of delayed periods.
Hope this answers your question.