Hi dr, yesterday i had some brown spots i feel it may be implantation and if so when can i take pregnancy test my next period is on 17/8/2014?

After missed period: Conception, as defined by the generation of a fertilized ovum, occurs within day or so of the sex. However, it takes about two weeks for the embryo to make enough HCG to produce 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. Negative result on a test done too early is not reliable.