Oo, possible talaga! A few of us moms experienced this, sometimes ang PT ay negative pa pero after a few days or week, positive na, especially kung very early pa lang ang pregnancy at mababa pa ang hCG levels. Since 10 days na kang late, mas better na mag-blood test na lang sa clinic para sure, kasi mas accurate yan kaysa PT, or try ulit ng PT in a few days with morning urine para mas concentrated ang hormones. Good luck, mama!