Yes, irregular periods decrease your chance of becoming pregnant. Many a times there is no ovulation when there are irregular periods. Also it is very difficult to know the exact date of ovulation when your periods are irregular. So calculating the fertile time becomes difficult. Some irregular periods are due to hormone imbalance. So this causes difficulty in the fertilized ovum to implant in the uterus.
Hence it is important to find the cause of irregular periods and treat them if you want to conceive.
High level of stress, dramatic changes in your life style, high cholesterol, hormonal imbalance as seen in thyroid problems and PCOS, chain smoking, may be some of the common causes of your irregular periods. Cushing’s disease and disorders of adrenal gland, tumors of the ovaries and adrenals, insulin resistance and obesity are some of the other factors.
You should consult a gynecologist and get this examined.