Welcome to the Pain Mangement Forum. I am sorry to hear about your pain.
You do not provide us with a lot of details in order for us to offer some suggestions. I would wonder if you have a spinal nerve issue? Sometimes the nerves in our spine can cause bowel related issues. I would assume the reverse could be true.
I think Millie is correct. Please consult your PCP. He/she can provide you with a clinical evaluation that will uncover why you are experiencing this pain with evacuation.
Please feel free to share additional information with us. Best of luck to you and please take care.
~Tuck
How long has this been going on and have you seen any doctor about it?