What Causes Severe Headache And Nausea After The Menstruation?

My wife go last menstruation on 28 nov, after that she was having pregnancy symptoms later now on jan 23 she started bleeding and majority was clots and cramps for 2 days and and 25 was less bleeding and from 26 jan 2015 there is no bleeding. she went to doc on 27th jan urine test was negative and 28 jan she was having severe headache and strong vomiting sensation.. please tell me she can still be pregnant now?