I had a 2-level (C5-7) ACDF last Nov and the biggest problem I had was muscle spasms, which sounds like what you are experiencing. As Ginnie suggested, specifically ask about soma or another muscle relaxant. The other problem I had was trying to do to much too soon. Make sure you are really giving your body time to heal. Rest and make sure you aren't unconciously lifting/moving too much or turning your head too much. I had numbness/tingling in areas other than the incision site for approximately 6 mos post surgery. You have to remember that the muscles and nerves that has been cut/stretched/abused are connected to a large network of nerves and muscles and those also react to what happened during the surgery. You may also want to ask about physical therapy if they haven't already talked to you about it. It's too early for doing a lot of stretches and strengthening exercises, but they can offer heat therapy, massage and electrical stimulation therapy at this point. That helped me a lot with the muscle spasms. Returning to work -- esp your kind -- at 4 weeks was probably not a realistic expectation; most articles on multi-level acdf suggest 6-8 weeks to be the average return, so don't let your current status alarm you.

Don't give up hope. It will get better! Best wishes!