How come some people never know they are pregnant? do they really never get a positive test????

Denial.....: is a powerful tool. It's more likely for a woman not to get tested at all than to have persistently negative tests. The majority of these "I didn't know I was pregnant" cases are young women whose parents don't know they've had sex, women who think they're too old to get pregnant or those with irregular periods. Obese women are less likely to appear pregnant, even to themselves. Helpful?