Studies comparing normal, healthy adults with chronic pain patients do report differences in reaction time, task performance, and attention span. In fact, chronic pain patients are slower in performing tasks during baseline conditions in most studies.
This slowed-down performance may be what you are observing about yourself. Researchers suspect that cognitive processes are impaired. Your attention is divided between the task and your pain or discomfort.
Attentional performance can occur as a result of interference by pain or just the threat of pain, other symptoms, or disability. Different people are threatened by different factors. Some whiplash patients are more threatened than others by certain positions and activities.