How do you know you have a bruised muscle, or messed up muscle?How do you know if you fractured something?

So I'm an avid runner. Unfortunately on February 6th 2010 I went sledding and injured myself. What i did precisely was i think the impact with my tail bone on the ground was messed up and I messed up some muscles. It's still hurting till today. Not unbearable pain though, its just ache, tight, and sometimes a sharp pain. Also I hit a tree with my leg and my back. So my muscles have been bothering me and my tail bone and also my back. Its not as serious as it sounds though because the doctor said i have no broken or fractured bones, but there was no x ray to verify it. I'm confused and want to run. I ran the past two days, and four miles each day. I lived through it.I want to get into top racing condition. Do you think this pain will just go away and I should run through it? Also What kind of problem do you think I have, since I know its muscular.... is it bruised or sprained? I really WANT TO RUN THROUGH IT!!!!! Could someone tell me how I can get through this?