My discharge is brown now. i was sexually active 13 days ago now. is this implantation bleeding? im 3 days late?

Bleeding can occur very early in a pregnancy and whether this could reflect implantation is pure speculation. If it did represent implantation a home pregnancy test should be positive, but it is a few days too early for a negative test to be reassuring.

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.