Any chances,for the pregnancy test to be positive after three days of ovulation and sex for a week . i tested and its negative. :(?

Too early: No chance of a pregnancy test being positive 3 days after ovulation, because that is too early. The baby embryo would not have implanted yet (that happens 5-10 days after ovulation, if the egg gets fertilized and turns into a baby embryo). If a woman has a newly confirmed urine pregnancy test, she likely would have conceived from an ovulation that happened 2 weeks or more in the past.

10 to 15%: Those are the chances to become pregnant per month providing everything else is fine if you try for one year and you are not pregnant you should see a Reproductive Endocrinologist.