Am 25 y.o. stopped bc pills on 12/16 due to nausea. had sex on 12/21 the guy did not ejaculate in me but pulled out. today i started spotting..is it too soon for implantation bleeding or is this more than likely my period coming?

Too soon to test: 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.