Can you take a pregnancy test 2 weeks before your period is due?

No. All the pregnancy tests require approximately the same amount of time including the ones at the doctor office. You will be throwing away money on negative tests if you are pregnant or not if you test earlier then the first day of your missed period. Waiting a couple days into your missed period is not a bad idea as your cycle length can fluctuate slightly due your luteal phase (time between fertility and period-beginning on next cycle)