I Have Had A Thyroidectomy And Thryoid Cancer Was Discovered

I have had a thyroidectomy and thryoid cancer was discovered in the pathology. I received radioactive iodine afterwards. I am having trouble with my bloodwork cause my levels are not consistent. I have also gained a lot of weight while all of this is going on. Last week I pulled a muscle in my abdomen during a coughing spell (I have a really bad cold that I have been to the dr. 3 times for) and they did a ct scan and didn't see anything, but did note a cyst on my pancreas and recommended a repeat CT in 6 months. Could this cyst be causing me a lot of my thryroid level problems and/or weight control problems?