Constipation is a common IBS symptom in those with constipation predominate IBS. Constipation is the inability to pass stool, while feeling a desire to and actually having stool that needs passing. It is usually caused by stools not being properly formed, being too dry or a lack of motility in the gut. Essentially it is the opposite of diarrhea.
Those who experience nausea as one of their IBS symptoms may be experiencing it due to constipation as hard to pass stool will slow the digestive system down & cause it to sends confusing signals to the brain.
Most cases of constipation will eventually resolve on their own. However those who have constipation predominate IBS will only get temporary relief from their IBS symptoms. Since constipation predominate IBS is a chronic condition, usually constipation will return again sooner rather than later.