I Have Become Increasingly Constipated Over The Last Three Months.

I have become increasingly constipated over the last three months. I also have my intestines jerking about sometimes severely. My doctor put me on Linzess. It reversed the condition but caused all day diarrhea. I am now on Miralax twice a day having stopped the Linzess. I am scheduled for a colonoscopy in early January. I have had IBS for the last 30 years but never experienced any of this before.