I don't know about itchy, but I definitely have felt my colon doing all sorts of weird things when my IBS is acting up. Also, when I eat or shortly afterward, I can feel more movement as well. The main part of my colon where I have pain or fluttery, spasmy feelings is also the descending colon area. I also can feel trapped gas in the middle (I think it's the transverse colon??) right under my rib cage. A good way to relax your colon is to use heat therapy...either a hot bath or a heating pad. It relaxes the muscles greatly.
IBS sufferers are thought to have heightened sensitivity in their colons, as well as greater sensitivity to feelings of pain and discomfort. What you are feeling could definitely just be IBS. However, you should go through all the testing to rule out other disorders whose symptoms mimic IBS. I wouldn't worry too much at present given what you are describing. If your symptoms worsen or change drastically, though, do call your doctor.