Hi sis! A false negative sa serum test means the test says negative (hindi positive) pero may virus/infection ka actually, kaya parang hindi siya nakita ng test even though you have it, if that makes sense? It happens sometimes kung very early pa ang infection or kung low ang levels, kaya marami sa amin na nabasa na recommended mag-repeat test after a few days para sure, lalo na kung may symptoms ka talaga. I'd suggest asking your doctor about this para ma-explain niya better based sa situation mo, they might want you to get tested again or do a different test para ma-confirm. Take care, sis!