Hi Bonnie! I wrestle with this issue also. When my chronic pain disables me to the point where I can’t function, I will take something to ease the discomfort. I don’t believe that God wants me to be laid up in bed, day after day, accomplishing nothing (even if I am offering it up). Chronic pain, while giving us an opportunity to sacrifice, can also drain a person spiritually. C.S. Lewis wrote extensively on the topic of suffering in “The Problem of Pain”. I found this book most helpful, along with Peter Kreeft, “Making Sense Out of Suffering”.
I find that if I have pain many days in a row, I become very depressed. It becomes much more difficult for me to do all the things I believe God want from me. Hope that helps!