Do I have a Mongolian spot?

I have looked up a mongolilan spot on the internet, and have looked at pictures. But I am not sure If what I have is a Mongolian spot. These spots are described to be a deep bluish/green spot. Mine are very deep colored, and look like spots with veins. Mine are located on my lower back and the middle of my left leg, and seem to be growing. Mongolian spots are flat, however my birthmark is bumpy at times, and other times are pretty flat. I have tried to see patterns in the change in texture, with temperature, and emotion, but there is no pattern. If you have any opinons, or advice, I would be grateful thank you.