I would think it's an irregular period if not you're too stressed out, because even if early pregnancy, the test kit would should be strong enough to detect Hcg levels, but better to get it checked to make sure no underlying
I have a friend who experienced the same thing as u. Menses never come for 3 months… She went to see a chinese physician and after consuming the herbs, it came. Dont be too stress! It might also be the reason