I've been searching for information on fertility, infertility, sperm, egg and all that jazz, on the web for some time now, and most of the websites say that sperm can live 3-5 days (not very good odds for 5 days), sperm can live for 7 days very very rare though and at that, it's not ever been proven that sperm that old can/has ever managed to fertilizes an egg! Sperm normally only last 3 days, can at a push last 5 days, if you have very good CM, an Egg only last's upto 24 hours at the most, some websites even say only upto 12 hours, Hope this helps! Chin up I hope you get your BFP soon!