testing for pregnancy shud b between 9 − 14 days post ovulation. a blood test can detect pregnancy as early as 9 days past ovulation so if u tink uv tested within the range I mentioned then ur test is probably — but if u tested earlier then take a home pregnancy test after u miss ur period of 14 days past ur expected ovulation date.
If it was 6 days after intercourse then yes it was too soon, You need to wait at least 2 weeks after intercourse before testing.... I would test again - try a home pregnancy test first, by now they should be able to pick up any HCG levels!