11 days since i've had sex my period was suppose to start three days ago instead i got implantation bleeding,blood test is negative,could i be pregnan?

May be too early to: tell. 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. You may wish to repeat the test in 4-5 days.