I did 4 pregnancy tests, 3 had faint line positives, today i started having n light brown discharge?

Blood test for HCG: If you do not get a regular period, you may wish to get a blood test for HCG level to settle the issue. 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. Use first morning urine.