How Can Stomach Pains With Irregular Periods Be Treated?

hi, i'm continously doing sex with my wife since 4 months.she not yet pregnent wats the problem. in mentions time she is facing stomoch pain and also irregular periods after marriage , first time period 2nd dec next month month 8th jan next month 11th feb and last month 18th march like that , whats the problem . please solve my problem sir