did you happen to go to a doctor for some tests? sometimes those apparatus to know that if you are positive or negative is not that reliable at all. sometimes there are instances too that you should do some 2 to 3 tests before you would get the accurate results.

sometimes all of those signs you think that you might be pregnant could be false alarm. consider your lifestyle of how busy you are or what nature of work you have. this may only effects of being stressed.

yes, stressed can be one factor too. being stress can lead you to a very excessive menstruation or you may have a skip of monthly period.

if you would really want to know what is the explanation for that, you better seek a physician's advice and consultations so you would get the right thing to do incase there will be.