Is it too early to do pregnancy test after 12 days of late period? does everyone experience implantation bleeding? if yes, when exactly it occurs?

No: Home pregnancy tests can show positive as early as 3-4 days after implantation. Implantation generally occurs 6-12 days after ovulation. So if the egg was fertilized right at ovulation and you used the most sensitive home test it could be positive at 9 days. On average it is 13-14 days after fertilization/ovulation when it is positive. Actually implantation bleeding is uncommon.