Are your periods regular? If so, then you may be prego, just that you could have ovulated later than you think. I would call doctor's office to schedule an appointment. I would also get them to da a blood test, so you can either rule in or out being pregnant. Good Luck.
maybe you didn't ovulate causing you to skip ur period for the month. if you've taken three test and they were all neg then odds are you aren't pregnant or you are testing to early, you can wait a while longer then take another test.