Who's had pregnancy tests give wrong result?

Hi! Today would be the 6th day of my missed period. I've been waking up the past 3-4 weeks feeling slightly nauseous (it will come and go throughout the day), mild indigestion/heartburn (never had this before). 2 weeks ago I had brown discharge that lasted about 4 days. I thought that could be implantation bleeding. I took 4 home pregnancy tests the last week and all are negative. Should I just keep taking tests?