Is it possible to have a false negative pregnancy blood test one week or two after unprotected sex?, period is due few days and experience cramping

Pregnancy ? A "home pregnancy test" will not be reliable if done "one week or two after unprotected sex", however, cramping prior to onset of a period may be due to implantation, and pregnancy is possible. Wait another 7-10 days and if no period, obtain a serum HCG test to be certain about pregnancy. .