Aw mama, I feel you! Honestly yes, it's possible, a few of us tried for months and got negatives kahit delayed na delayed, tapos one of my mum friends got her positive on day 14 of her delay kaya hindi ka nag-iisa dito. The thing is, ang hCG levels nag-start super low and it doubles every 2-3 days, so kung nagtest ka too early or if your levels are just building up, ang PT really can miss it. Since you're 11 days delayed na and you're feeling symptoms, I'd really suggest makipag-consult na sa doctor para mag-blood test instead, mas accurate yan at makikita agad if there's anything going on. Fingers crossed for you, sweeeet!