Tmi warning

Ok. So I am in my fertile days and I know that when you ovulate you can sometimes have bleeding, I usually have a spot or two. This month though it is different. I am having dark brownish spotting that is a lot heavier than it usually is and my CM is practically nonexistent. I have endometriosis and have been TTC for 6 months. Starting to worry about this because it is new to me. Anyone know what is up or have this happen to them? Thanks in advance.