Could Delayed Periods With Spotting Be The Symptoms Of Pregnancy?

I m 6 days due for my period. I got pregnancy test done 3 days ago, it said negative. Also, I only bleed few blood drops after I am done urinating! I don t feel like frequent urnation, nausea, dizziness, etc. But I have severe backache since a week. I have had unprotected sex a couple of times since a month. But he didn t ejacuate in me once. I don t know what wrong because I have never had irregular periods.