My period was on 5 sep and did sexual relationship on17 sep and that day taken unwanted 72 tablet aftr that on 1to 3 oct my bleeding came and on oct 24 to 25 only two days bleeding came,in betwn that i checked pregnancy test but it nagative , i'm pre?

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.