I had my period on January 5-7 then I started cephalexan (antibiotic) Tuesday January 12th and ended it January 16th. I had unprotected sex January 22nd and he ejaculated in me. I took the my way emergency contraceptive pill 5 hours later. I did not get my period on January 31st as planned. I've taken four pregnancy tests 11,12, 15, and 17 days after unprotected sex, but I know that could be too early to detect any pregnancy hormones. It has been 17 days since the accident and I am exhibiting no unusual symptoms other than the missed period. I am very worried please help.