Faint line on HPTs, negative blood test

So, I'm getting so confused about the whole pregnancy test thing. My period is 13 days late(I've never been late, cycle has always been regular) and for 2 days now I've been testing with a pink dye test and been getting very faint negative results. Went to the clinic this morning to get a blood test, twice they came back negative. Doctor said I should go home and come for retest in 2 weeks time if aunt flow doesn't show.

I don't know if anyone has had such experience of faint urine test and negative blood test and still ended up pregnant and with a healthy baby. Do help a confused and desperate one.