Hey mama, I understand your worry kasi first time talaga na ganito, but honestly 10 days delay with negative PTs could be a lot of things, sometimes stress, hormonal changes, or just your cycle adjusting pa lang, especially if you're still breastfeeding your 1 year old. A few of my mum friends had delayed periods months after giving birth and it turned out normal lang. But since you're really worried about it and the uncertainty is making you anxious, I think it's best to see your OB para ma-rule out everything and get proper peace of mind, they can do a blood test which is more sensitive than home PTs. Sending you a hug, it's stressful not knowing, but you'll get answers soon!