My period is late (8jan). i did a pregnancy blood test on 4 jan came back negative cause i had sore breats & constipated & dr had prescribed me a colo prep that week. 10jan there was a brown discharge but now back to normal?

Blood test for HCG: 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.