Anyone only get a positive from a blood test?

Ky 8-15-17👼🏼 & 10-28-17👼🏼 Pregnant with my🌈💕
Has anyone gotten negative pregnancy tests and only test positive from a blood test? I am a week late for my period as of today and I keep getting negatives. My last few periods before this have been on time. So I don't understand.