Spotting all the time

Hello everyone,

This is my first time posting something here. I have been trying to get pregnant for the past 4 years. I had 4 miscarriages. Every single one terminated very fast. My doctor found a small fibroid on the outside wall of my uterus about 2 years ago. I have no extra bleeding or pain at all due to the fibroid. But about 6 month ago I started spotting in between my period all the time. The color is different but it’s constant. My doctor doesn’t know why. Does anybody have any idea what might have been happening with me??