Whipple procedure

My father was diagnosed with colon cancer in 2006 and had a whipple procedure surgery shortly after, He was in the hospital for 3 weeks after because his body wouldnt wok on its own.is there anyone out there that can help us to figure out what to do about the pain he is in 2 almost 3 years later. He has moments when his legs hurt so bad he can not even stand up ( mostly when he is using the toilet). He is going to the bathroom between 3-6 times a day lasting as long as 30 minutes a time. Also his dr has him taking vitamin D and we arent quite sure what its affects should be. His body isnt absourbing the vitamin from the sun or foods we know that but not sre why, If anyone has had this surgery and have some of the same issues can you please help us to understand what is going on or what we should do about it. we ;ive in southern oregon and we have a great cancer center here but its hard to get in when you are not really sure whats wrong or if it is really wrong......I am very worried about my dad because it also has made him very depressed