I Have Had A Terrible Pain On My Tailbone For

I have had a terrible pain on my tailbone for a week now , I can barely sit and it's painful to walk . I noticed that the skin around my tail bone had hardened and is extremely sore and painful . I've gone to my doctor who sent me to the ER , but they told me there was nothing they could do . No pain killers are working , what is wrong with me ? What can I do ?