Why do I have constant rectal pain and who do I see?

Colorectal surgeon. See a colorectal surgeon for a proper history and physical exam. A number of things can cause rectal pain and correct diagnosis is key to effective treatment.
Please see your Dr. There are a number of possible causes for rectal pain; the only way to determine the diagnosis is to see your doctor. Your doctor will need to examine the outside of the anus and will likely need to do a rectal exam as well. If your doctor does not find a cause, seeing a gastroenterologist (gi specialist) would be the next step.