I'm Wondering What Types Of Muscle Disorders There Are Or

I'm wondering what types of muscle disorders there are or what type of doctor I should see regarding severe, chronic muscle pain in my legs (calves, thighs - basically entire legs; Right leg dominant) and severe, chronic pain (and what feels like muscle pain) on both sides of my lower back. Initially I was dx with MS, but my new neuro is not sure now. He is running more tests. I'm just curious about the severe muscle pain which has been going on for about 7 years. I take 60mg morphine twice a day and I still have severe pain. I do not want to continue taking pain medication or increasing the dosage. I am so depressed, in pain and feel no one is really listening to me and where my pain actually is and the true severity of it. Thank you for your time. FYI, I also had a grand mal seizure 18 months ago (several of them) and suffered a small heart attack due to the violent convulsions. I see a cardiologist every 6 months. I am a 47 yr old white female. Thank you for your time.