I Had ACDF Surgery On Levels C5/6 And C6/7 About

I had ACDF surgery on levels C5/6 and C6/7 about 6 months ago to treat herniated discs. The nerve pain I had once had has improved a lot, it would feel like a hot stabbing knife in my back on the left side. But what has happened since my surgery is I am having terrible muscle spasms in my mid to lower back in the paraspinal muscles whenever I am somewhat active ie standing, carrying objects, washing dishes, etc. What can I do to prevent these spasms and what can I do to alleviate the pain and spasms once they come on. It seems nothing at all with help. Even with laying flat or complete rest the pain and tightness are unbearable.