[Always *]

Well, if you just had sex like the week before the soonest point you'd expect you're period, it is very likely that, sure, you could of missed your period if the egg already implanted there, but that you're bodies hormones haven't caught up and started changing and the "baby growing processes" wouldn't be in full swing yet (thus causing a positive test and overall pregnancy symptoms). And sorry if "baby growing processes" isn't the most analytical sounding way to put it. But, even if it is to early to receive a positive test (which I don't see how that is all probable if you're body can be bothered to miss a period over it any how) like everyone else has been saying, you really don't seem to have a reason to worry to much quite yet over being pregnant, you have no other symptoms and negative tests to show for it, and you should probably just relax a teensy bit which may help it arrive. People can miss periods for a lot of reasons, like stress or with massive changes in diet and lifestyle, if it doesn't come and you proceed to go into the next window where you'd be expecting yet another period I would most certainly go see a doctor and just ask him/her to do a pap and/or pregnancy test or anything else to make sure your lady goods are healthy and baby free, some of those like a pap might not even be necessary if the doctor has a simpler answer that'll allow you to keep your pants on though but that's not really my point