What Causes Light Menstrual Bleeding?

Hi. I am a 21 year old woman. I have had 2 miscarriages my last one was on 3rd of April this year. On thursday 14th of July I was meant to get my period but instead I got it on the 10th well it wasnt like my normal period as it was more of a mucus mixed with blood at the start it was light blood and at night it was more brown it wasnt heave as I only used about one pad for the whole day. On Monday it was already gone. On Tuesday I had light bleeding only few drops and it was gone within an hour. On wednesday night I got light bleeding again it was gone within two hours the same on thursday but those both day it was only visible on toilet paper. It was gone until Friday and the same again but this time visible on a pad but just few drops on Saturday when I woke up it was again visible on toilet paper and gone within an hour. I have taken a pregnancy test but it was negative can you please advise what should I do in this case?