What Causes Severe Menstrual Cramps?

Doctor,My wife age is 33yrs old,working in Nurse,one year before marriage finish.Her menstrual period duration above 60days(eg:22,sep'2011 next 22,Nov'2011)above 8yrs,every menstrual time she will feel severe pain.Her chance to give baby....My wife consult to many doctor since 8yrs,but all doctors are said after marriage it will cure.But,still she have same problem...what is the cause...?.She will give baby or not.when her pain will stop..?.Please give me answer