Yes. Emotional stress is extremely disruptive at many levels, including mood, but the body's responses are quite varied. One of the most common areas to be involved is the GI tract, so stomach pain is often present. Of course, other things can also cause pain, including things like ulcers, which can result from stress. Stress can involve any part of the body. Many stress reduction techniques can help.
Possibly. Gastrointestinal symptoms, such as stomach cramps, nausea, diarrhea, constipation can be caused by anxiety. If anxiety is the culprit, then seeking the care of a psychiatrist or psychotherapist would be helpful; however, it is very important to see your general doctor to rule-out non-psychiatric causes of stomach pain first - such as infection, reflux esophagitis, inflammatory bowel disease, etc.