Me and my boyfriend have been trying to conceive for a few months now, but so far we haven't had any luck. I should have started my period 2 weeks ago but I haven't. After the first week I went and bought a pregnancy test. The first test came back negative so I figured I'd probably start my period in the next day or two. Now it's been two week and still haven't started so I just took another pregnancy test and it's still saying not pregnant. Should I be concerned??