A few questions come to mind:
Any family hx of cardiac disease?
Any other concurrent medical problems?
Date of last good check-up, including blood pressure, cholesterol, TG levels, etc?
Where in the chest is the pain? Is it with only with inspiration or is it constant?
Does it truly only happen, as you say, during the first 3 weeks after a cycle or has it ever happened at some other time?
Have you ever had it evaluated, especially during the time in which it was happening?
Need some more info here.