Extremely tired after several chemos and a constant urge like need to have BM.

I am writing for my dad (60 year old with colon cancer and mets to liver, inoperable and radiation not an option) He has a constant urge like he has to have a Bowel Movement, even after he has one. It is causing him alot of pain and discomfort. Anyone had any experience with this? He is on tons of pain meds and nothing seems to help. He also is extremely tired before, after and during chemo. He has had about 13 rounds of chemo. It started with Oxyplatin but now he is on fu5. He is just so tired and miserable all the time. He has a rotten quality of life. he never gets out of the house except to go to chemo and is living onthe couch. He hasnt driven since diagnosed in October. He just says the pain is too much to even move. He is on fentynol, oxycotin time release, oxycodone for breakthru pain and is still miserable! Any ideas?