I started on Avonex and switched to Rebif and have been on it for around 10 years. It's 3 shots a week instead of 1 but the needle is smaller.

I think Avonex may have an auto injector now but Rebif has had one since shortly after I started it. I like it better. :)

I think that Rebif is just shot under the skin and
not into the muscle, as Avonex is.

That is correct. Rebif is subcutaneous (just under the skin) 3 times per week. Avonex is 1x per week intramuscular (into the muscle).

Sounds like you are okay with the outcome, but just wanted to put this out there just in case...

as a last resort, you could consider involving your employer, if you feel comfortable with that.

Hope everything works out well for you :)