Hi Suzq...I'm Jenny and I'm fused from C3 to T1. I've had the exact same problems you are having now and I did find some solutions other than drugs.
The intense muscle pain comes from the fact that the muscles no longer move. The fusion makes them useless and they ache...horribly. Same with the headaches...muscles that aren't working anymore and ache and set you up for muscle tension headaches that beat whatever you ever had before. I was never one for headaches and now.....
The arm pain and weakness is most likely from whatever made you need the fusion in the first place. My doc was very careful to explain to me before surgery that once compressed, whether it be spinal nerve or spinal cord, the damage is halted but may not recover or may partially recover. I stayed with the arm pain and weakness and now, 3 1/2 years out, I've developed loose tendons in my left arm that causes my joints to dislocate.....again, the nerve damage has slowly gotten worse and is showing it's effects slowly but surely.
But here are some on the things I found that helped so much so that I don't take any pain meds at all.
For the neck muscles.....I found at PT that when they used the electronic nerve stimulator, it exercised the muscles that I could no longer use and the pain went away. I did this 2 days a week for several months and eventually, the pain subsided. If it did continue, I was going to purchase my own machine and learn how to use it so I could plug myself in daily and let it exercise those muscles until it got all the lactic acid out and let them relax. Helped with the headaches too. Come to think of it, I just may look into one of those machines yet...I may be going for more surgery shortly to extend the fusion and remove a lot of bone spurs hitting my cord again.
For the weakness, again, it was PT. tThey had me very slowly work the muscles. At first they did it by holding my arm and moving it through the full range of motion and then letting me push against resistance. I slowly advanced to doing my own exercising and it really helped. The muscles got stronger and I got less pain. Sounds counter-intuitive but my neurosurgeon again agreed that exercising the muscles releases the acid in them and makes them hurt less while slowly making you stronger. So I got stronger muscles and less pain. Now I head for the garden and do some good hard yard work but I do it in 15 minute spurts with lots of rest in between. It works the arm muscles and then they relax and the pain goes down. But I carefully watch my neck at the same time. PT taught me how.
I have gone in and out of PT since surgery which was 1/11/07. I've already let them know I'll probably be back with more surgery but I even went back earlier this year for some specialized PT on balance. The long fusions give you poor balance. It worked.
So find someone who does a lot of work with people with spinal problems but especially neck problems. I found a PT who had back surgery herself and was married to a spine surgeon. What a find! She developed exercises just for me and went so very slowly it never aggravated anything.
I know I'll be using PT for the rest of my life just to get some good muscle work done and find out the latest in treatments. And I may still buy an E-Stim(as they call it)machine for home use. Make sure if you want to try it that your doc ask for that by name.
There is life after cervical fusion.