I did 4 pregnancy tests. 3 is positive but the last one which is digital, is negative?

Play it safe: I would recommend treating yourself as pregnant until a doctor clears you with an office based test. Take prenatal vitamins (they won't hurt you if you are not pregnant) but can make a huge impact early on in pregnancy.

Blood test for HCG : 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.