What Causes Pain In The Muscle Associated With Swelling?

Question: heres the question. I had an attack of what seemed like my muscles, nerves in the flesh on my back that was much worse than ever. I am sensitive to drafts and cold air on my back and will have a little pain an aches all over this area. But at first felt like a bad flu with no flu symptoms. And CONCENTRATED pain in my back, VERY UNCOMFORTALBE. After a few days, I was able to get around, not in bed but that concentrated pain kind of burst and I was in pain all over the fatty, fleshy parts of my back, front and back of my shoulders, under upper arms....so painful and I check my sides....my left side was so swollen from spine across front moving up with what felt like a fat rod there too. I took magnesium and after a week (not sure if it was magnesium or worked itself out). It felt that instead of tense muscles, my muscles relaxed and would not closed....so it felt. I have had this before but this was this was HORRIBLE. Drs. office did not have close appt. Is this muscles, nerves, or neuropathy or what could this be. I am wearing two heavy pullover sweaters in the house to keep my back warm. Feedback please. Thank you.