Ay, mahirap talaga ang situation na yan, lalo na kung EBF ka pa! So honestly, kahit delayed ka for 2 weeks and negative ang PT, possible pa ring buntis kasi sometimes ang hormones from breastfeeding ay nakakaaffect ng cycle, pero alam mo ba, a few of us moms got false negatives early on kaya best talaga to retest after a few more days or check with your OB para sure na, mas makakatulong siya mag-confirm either way at makita if may iba pang nangyayari. Stress din sometimes causes delays so don't panic muna, but yeah, doctor visit would really help you get peace of mind, lalo na 9 months postpartum ka pa lang.