Hi mommy! Implantation bleeding is usually super light and short, most of us mums I know who experienced it said it was just a day or two of brownish spotting, nothing heavy like a regular period. Four days onwards with light brown spotting could still be implantation, pero honestly kailangan mo talaga mag-check with your doctor to be sure, kasi could be something else din or maybe your cycle lang. Best thing is to take a pregnancy test after a few more days or visit your OB para ma-confirm agad, para you'll know for sure ano exactly ang happening. Fingers crossed for you, mama!