Need help..

M

Could someone help me understand this? I have been having visible lines which you can see on the picture. Then today the line is barely visible. I took my IUD out last month, after having it since 2014, no period at all during that time. So I’ve just been trying to track every day to see, but I’m confused. Just looking for a better understanding. I know if the line isn’t as dark or darker than the control line than it’s negative.