Most of my symptoms have been on the left side too. I've had the weakness and the buzzing, electrical sensations in my left foot, etc. I was also tested for Lupus and it came back negative. I have a brother and a cousin with MS so that was a huge worry of mine. I'm going to wait several months before I pursue that testing since I think this is all Mirena related.
Anyway, I've had mine out for a little over two months and I just finished my second period post removal and I noticed a significant improvement after that. The left side weakness and vibrating has been practically nonexistent since then. I am still having a lot of joint pain, but most things have been much better.
The left side thing is really weird. I don't know why a lot of people have left sided symptoms. Strange stuff.