Both of my pregnancies I knew within a week, just that something felt different. My first visit to the dr to get a test showed an obvious negative until he leaned back in his chair while holding the test. At a certain angle there was a slight sign of positive, you had to tip the test back and forward to see it. He told me that I was "slightly" pregnant. Told me to wait 2 weeks to come back. Less than a week later I was suffering severe side pain so went back to the surgery, got a different doctor and had the same result in the test. He told me that I wasn't pregnant and to come back in 2 weeks. I waited 3 weeks and went to my regular doctor, the test this time was a definite positive.