False negatives???

So I'm not sure where to post this but I gotta question... I know it's unlikely to get false negatives unless you test to early of course but has any one ever gotten an actual false negative even when it was not tested early? My friend thinks I'm pregnant because I'm missed my period by almost a week now the last four days I have been extremely nauseous and it's getting worse day by day but by late evening I feel fine.... I have taken test though they all keep coming up negative I have taken first response, clear blue and equate ones ( I stopped the equates one bc they always looked postive even tho the rest came up negative but I think they where evap lines) she wants me to get blood test done but I don't want to waste my time only to be disappointed....