Wa'alaikumassalam! OPK tu memang akan jadi lighter or negative bila dah pregnant, sebab hormones berubah completely lah, a few of us tried OPK lepas confirm pregnant and semua came out negative je, so don't worry kalau tiba-tiba jadi negative after positive sebelum tu. Once you've conceived, progesterone naik and the LH surge yang OPK detect tu tak muncul already, that's actually a good sign!