What Causes Intense Pain In Tailbone And Low Grade Fever While Having Lupus?

First, I m going to start with I already know I have lupus and was diagnosed about 9 months ago. For almost three months I ve been taking plaquenil and 81mg of aspirin because I also had a positive LLI, lupus anticoagulant. A couple of days ago, I started getting annoying throbbing behind my left knee/upper calf area. I also have a history of pluresy which causes pain in my chest and my rib area. I ve been experiencing similar symptoms, but this time without having the cough. Last night I started having shooting pain down my left arm and my left shoulder blade was hurting. Today most of that seems better, but now I m having this intense exchrushiating pain in my tailbone. It has been hurting all day, but standing up, walking or coughing and sneezing seem to intensify the pain more than sitting or lying down. I do not have a PCP as she recently left or possibly was asked to leave the health care facility I go to. Urgent care doesn t really seem to help with complicated cases, they re primarily for the common cold, ear infection or broken bone. I hate the idea of going to the ER because although I m hurting I don t know that I m truly having a medical emergency. Any thoughts or suggestions. One last thing, I ve also been running a low grade fever.