MISSED Period but negative urine and blood tests

My cycle is 30 days in length.I have taken many tests,which were negative.Im very confused as ived never been late before.What other options do I have at this point.My last menstrual cycle was January 18,2017.Please help me before I begin my BC packet.And I am having symptoms as I have had with my first two children.Could it have been stressed?If so how can I get my cycle to start again.Very Frustrating for me,someone give some clarity