I too struggle with side effects from Avonex. NHE gave me some good suggestions, so his post is good stuff.
I have had ms for about 8 yrs and for the first few, it was almost "benign". I didn't take anything, not even steroids for relapses, and I always fully recovered, so my edss would move between 0 and about 3 or 3.5, and I didn't really miss any work. I was never offered any treatment and didn't really know anything about what was used.
This past year has been tough - I had 2 really bad relapses and was admitted to hospital for iv cortisone. I did not recover from the first one, then had another about 6 weeks later, from which I also did not recover (my edss was sitting at about 5 or 5.5).
I began Avonex in Feb, and at first the side effects were terrible! They have settled somewhat with ibuprofen (big doses!), but I still have major issues with increased muscle spasms and spasticity from the interferon (it makes those particular symptoms worse) and terrible pain.
I now take baclophen 10mg three times a day (in addition to the ibuprofen) on the day of my shot and the next day, and then 5-10 mg once or twice a day for the rest of the week. This hasn't completely erased the side effects, but it certainly helps. I also inject in the afternoon, as it is worse if I inject at night (same as NHE) - high fever, chills, sweating, bad shakes and spasms....I take neurontin and amitriptyline every day for neuropathic pain too, and this may also help on the day of my shot. After 8 or 9 months, I have good shot days when I don't feel too bad (with all my meds), and I sometimes have bad shot days, which take me back to how I felt at the beginning of treatment - so it definitley gets better over time!
I must confess that I have also wondered if it is worthwhile taking it, but I have been stable since starting it and will persevere, I think, for another few months to see if things improve...
I hope that your ms follows the same course as your mothers - it seems as if it will, but there is so much uncertainty around this disease, it is a bit of a gamble. NHE stated that the efficacy of Avonex was only about a 30% reduction in relapses, so you really need to weigh that up against the way it makes you feel - only you can make this decision and it is a tough one. Your neuro is obviously concerned and trying to act in your best interests (you are fortunate!), but he doesn't really understand how you feel - maybe you can discuss this with him further, and there might be some other medications to help you deal with the side effects that you can try that might help you through the next few months until it settles a bit?
I am sure you will make the right decision - and I wish you well.