What Causes Skin Bruising?

My skin feels very bruised everywhere with no sign of bruising. I have RSD and have experienced this before but it was only in the back of my arms and as far as I know its not a symptom of RSD.. but than again they learn new things about it everyday. I am worried if it is the RSD it means a flare is about to happen which would make sense due to my surgery a month ago to get my stimulator removed. But my neurosurgeon took all precautions during surgery including inducing me with Ketamine. If you have an ideas that would be helpful I would greatly appreciate it.