What Causes Delayed Period While UPT Is Negative?

Hi, may I answer your health queries right now ? Please type your query here...hi I'm quite worried I have worked out I am between five and nine days late for my period I'm never late! Me and my partner have been trying for a baby yet I've had problems in the past and it took me years to concieve with my little boy now two• I have done home pregnancy tests yet there negative