What Causes Unexplained, Spreading Bruises On My Stomach That Aren T Fading And Are Growing In Size Without Any Injury?

I have several bruises on my stomache region. I ve been keeping watch on them, and they are not going away. When I woke up this morning, there was another cluster of 3 round bruises that appeared overnight on the left hand side of the right hand side of the original cluster of bruises. The bruises are not changing to a lighter color. It seems as if they are becoming darker in color and spreading from side to side. I started with one bruise on my stomache and that bruise was about 1 inch by one inch in diameter now its 3 1/2 inches wide by by 1 1/2 inches tall. There was no injury by accident or otherwise to the area.