Spotting and negative upt

Hai saya nak tanya. 4 hari lps, saya spotting. For 2 days. Mmg brown and kecik gila. Pakai panty liner pun tak penuh langsung. So mmg obviously spotting. Tp saya test upt asyik negative je. Period pun dah lewat 2 hari ni. Siapa kat sini yg spotting pastu pregnant, amik masa berapa lama bqru positive?