Uy mama, I feel you, three weeks delayed is honestly stressful, and ang mahal talaga ng PT ngayon! But honestly, if you're 28 days delayed na and took one at three weeks, that should've shown positive kung talaga kang buntis, so the negative is likely accurate. That said, since you have PCOS history and your cycle can be tricky even if regular lately, best to check with your OB kasi they can do blood work or ultrasound to be sure, mas malinaw at stress-free na, hehe. A few of my mum friends with irregular periods din went straight to the clinic instead of buying multiple PTs kasi mas guaranteed ang peace of mind, at alam mo na agad kung ano talaga. Fingers crossed for you either way, sis!