Is your cycle regular? If yes, then I suggest you take the blood test for a more accurate result. Happened to me before. My cycle is regular and once I missed for 2 weeks. HPTs all showed negative. Took a blood test and it was positive but HCG was very low. Turned out to be a chemical pregnancy. Body rejected the cell. Tried again two months later and I finally conceived. dear son is 6.5mth now.