The muscle problems you describe are often part of polymyositis or dermatomyositis. It is common for lupers to have an overlapping connective tissue disease with one of them. You should note all your symptoms and see you rheumy as soon as possible. Myositis is treatable but needs to be diagnosed and then aggressively treated.
Are you having swallowing problems?
NSaids will help with your joint pain but prednisone is the most powerful anti inflammatory agent and will help by reducing the swelling as well as "tranquilizing" your immune system. Imuran is good to control your immune system but it takes many months to reach full effectiveness and it sounds like you need prednisone for aggressive treatment. What dose did your doctor put you on?
Mixed connective tissue disease (systemic lupus, scleroderma, polymyositis), Raynauds phenomena, Hypertension, Barrett's esophagus.
Meds: prednisone 5mg, 50mg imuran, Lotrel 40/5mg, maxide 37.5/25mg, folic acid, potassium, aciphex 20mg, multi vitamins.
Maintain your optimism and you can beat the odds.
"Although the world is full of suffering, it is also full of the overcoming of it." Helen Keller