Could Delayed Periods Be Due To Pregnancy?

i feelso pregnant my last cycle was between dec 23rd - 26th i have alwon a 28 day cycle i have 3 children and i know what pregnant feels like had a blood test over a week ago and all my doc said is it was normal thyroid etc all fine urine test neg....i have all the symptoms of preg... I have never been late except during pregnancy..unprotected sex all month ... what do i do