I can imagine how scary this must be. I had a weak left leg and hand all day yesterday. Also a few numb toes and fingertips. It's gone again today. My mirena was removed almost five weeks ago. I think it may have something to do with the ovulation, since I will hopefully get my second period in about two weeks (first one was 2 weeks ago). But, however, I think you should get some medical advice.
Do you have any history of migraines? Those can cause the same symptoms. Or hyperventilation, anxiety. Do you take anti depressants? Do you have any other symptoms apart from the weakness?
Here's an interesting link:
Perhaps this will ease your mind a little. But still, I think you should call your doctor anyway, even if just to ease your mind. Take care.