What is the cause of my bloating/constipation/incomplete bowel movements?

[MichaelMartin]

I suffer from the feeling that my bowel movements are incomplete. Thanks to the fiber supplements I take, I am able to go regularly enough and produce decent-sized stools most of the time, but there is a feeling like I have a lot more that I can't get out. I rarely if ever feel empty/cleaned out after a movement. I regularly feel bloated and burping. I also know I have hemorrhoids. Could the hemorrhoids be causing the problem, or is there another cause?