I took a pregnancy test 2-3 weeks after intercourse, which was 4 days after what i think was my period (hopefully not implantation bleeding) started. it was negative. i used clearblue digital ultra early test. how accurate are the results?

Detecting human gonadotropin (hCG) in the urine is fairly accurate depending on when you take the test in proximity to missing your period. For more information, check the manufacturer's website https://www.clearblue.com/pregnancy-tests/early-pregnancy-testing

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.