One of my legs has been aching for days? It is a dull ache, like it's really sore. It's constant, not unbearable, but always there. I don't think I can stand anymore of it! What could this be? Edit ...
My guess is a blood clot. That can be serious if the clot breaks loose and goes to the lung. http://www.nlm.nih.gov/medlineplus/ency/article/001108.htm