My experience of Avonex was that it was the only thing offered at the time and caused a weekly depression and in my view is an antiquated poor treatment option. There are far more effective treatments available that will help prevent disabling relapses rather than allow MS to smoulder. It’s too late when it fails which it will as the effectiveness is questionable. I am sorry to be so emphatically negative but it is a bit of a crusade of mine to encourage folks not to even start CRAB drugs. Even if you are wanting children there are other more effective options. But it’s your life and your choice.
I suggest you look at videos by Aaron Bolster or read Dr Giovannis opinions on the drug choices you have been offered.