Delayed or irregular periods can be because of hormonal imbalance, PCOS, ovarian cysts, sudden weight gain or anaemia etc. Also your wife has dealt with local issues like polyps. And you have already tried for more than three years. Hence you will need a thorough evaluation regarding the factors that are preventing a pregnancy. Blood work, hormonal panel, ultrasound can, semen testing and laparoscopy should be done.
Consult a gynaecologist and an infertility expert for an evaluation.
The answer is based on information provided. Exact advice is not possible without a proper examination and investigations. You are requested to consult your Doctor. Take care and keep us posted.