Tysabri and Chest Infections - help!

Tysabri and Chest Infections - help! I’ve been on Tysabri for 7 months now and I’m looking for some advice and feedback. I never experienced ANY side effects, which I was very happy at and even by the 4 infusion felt really good. I felt very positive after that infusion as I felt my starting Tysabri was the right decision after all. But last month on which was my 6th infusion I took a really sore throat that night - which then just got worse, grew arms and legs and became a very nasty chest infection. So far I’ve had 2 lots of antibiotics and 1 course of steroids and the bloody thing still hasn’t entirely shifted. Every time I breathe I just hear a crackling from my chest and throat and Im just absolutely exhausted and sore. I called my Neurologist last week to let her know and she advised me to contact her again this week for an update. Have any of you experienced this? I feel really down as I was very ill last year due to 2 really bad relapses which left me in a wheelchair for a few months. I just wanted to remain positive about this year but so far out of the 9 months so far - I think Ive felt ‘ok’ for 3 of them! Any advice you can give will be greatly appreciated. Steff