Hi Ro,
I totally agree with Bob in that you are still in the early stages of your recovery and with my first surgery....I, too, had to wear a collar for about 3 months...This in itself caused a lot of pain and "burning" in my muscles towards the end of the day because your poor neck doesn't know whether to "lean" and rely completely on the collar or to use it's muscles to hold your head up...

So, it's at that in between stage and since you're not relying totally on your own muscles to build them back up after surgery....it will take some time...Did they use metal plates and screws to help with the fusion??? My first sugery they did not and this is why I used the collar for so long.....The last two surgeries....i have lots of metal, rods, plates, and screws to help fuse and didn't have to use a collar at all....But every surgeon seems to be different....
I would also say that when you are done with the collar....you will probably still feel some residual muscle pain/burning as your muscles are re-learning to all be used again...
This is a great time to work with your Dr. on continually stepping down from your medication and doses to let your body get used to handling the regular aches and pains that can happen....I know for me, by the end of the day still....after about 4 months out from this last surgery (they went in from the front and the back of my neck so cut through muscle in the back)....I spend my evening resting my head on the back of the couch with my favorite pillow.....it feels SO much better just to "lean" against the back of something after my neck muscles have been working so hard all day....
Although you think with my head full of air...it would be really light...HAHAHAHA....
Sorry, couldn't resist.....LOL...
Please give yourself time....a fusion actually takes a total of a year and there are many tweaks of pain/soreness that can happen from time to time and also when you start getting more active and then tapering off the pain meds.....