Ah sis, nakaka-anxious talaga yan especially pag negative ang PT pero late ka pa rin! A few of us moms went through this din, sometimes it's stress, hormonal changes, or even just our body being weird, kaya best talaga mag-follow up with your OB para ma-rule out kung may iba. They can do a blood test which is mas accurate sometimes than PT, lalo na if super early pa ang period mo or may timing issue. Keep us posted ha, I'm rooting for you!