Is bulge in middle of lower agdomen from enlarged bladder or colon?

Can be/other things. Depending on your age, etc. Other things, like weak ligaments that hold up the bladder and other organs can cause fuller/lower feeling bladder. A distended colon can do it, but depending on the cause other symptoms would be present, like bowel disturbsnces, etc.. In women, things like ovarian cysts, etc. That enlarge the ovary can increase the abdominal size/girth. See your doctor to be sure.