What Are The Early Signs And Symptoms Of Pregnancy?

I feel pregnant, My period is 4 and a half days late... I take 20mg of Citalopram, we are trying for a baby & my last 'period' was very very light... I have done a preg test (one I buy online) and it was negative but Im sure that I am pregnant? Am I just wishful thinking? Or is there a chance I am? Could my antidepressant effect results?