Can cause irregular menstruation pain inthe center of the chest and in thearea between the shoulders, often painspread inthe left shoulder, rare inright?

Pain: If i read your question right you have irregular menses and then you have pain in center of chest and then to shoulder blades. The irregular periods are a sign of hormonal issues. I would be suspicious of thyroid problem. As to your specific pain substernal pain should always be checked for possible heart problem. However, i would be highly suspicious this could be gallbladder.