IVIG actually helps with immunity as it contains the antibodies of hundreds of people who donated their blood to make it. It, however, isn't foolproof and infections do occur, especially since you have pred on board.

As you are learning, or already know, infections can make MG unhappy. The IVIG is still there, but would naturally be starting to "run out" of activity since it's been over 3 weeks since you received it.

I would suggest you give your doctor a call so this can be documented. I suspect you will be looking at adding another immune suppressing drug, such as imuran or cellcept eventually, as most with moderate-severe symptoms need that if any chance of work oriented life is desired.

Sorry you are feeling badly. Hang in there!