Just venting

Period is 2 weeks late, negative blood test. Dr told me to call back if I didn't start in the next 2 weeks. I have always had regular periods so I have no idea what's going on. Had an ultrasound last month and she said everything looked good. Anyone have experience with this? What could it be? We're you still able to conceive. This will be our 7 month trying and I feel like nothings working. If I don't have a period then I'm not ovulating so there's no chance to get pregnant.