it could be from spasms in the colon which is common at the point where u describe .
The small intestine absorbs nutrients from food and passes undigested food into the large intestine. In the large intestine, or colon, this waste product is processed into faeces.
The normal bowel moves food along the intestines through muscular contractions, known as propulsion. There are also areas of hold-up, known as segmentation.
This combination of propulsion and segmentation is called peristalsis. You are completely unaware of it when it is working normally.
The control of peristalsis is complex. The best way to regard IBS is as a loss of coordination of these muscular contractions.
In addition, there is evidence that people with irritable bowel syndrome have increased sensitivity within the gut to external stimuli such as stress.
sometimes anti spasmatics can help with this and more fibre and water in the diet