Thanks for your query
is a emergency contraceptive pill
and has side effects like making the periods irregular so continuous use should be avoided.
Since your wife has taken 4 I-pills in a month it is bound to make her periods irregular.The problem with her right now is more likely to be a hormonal
imbalance and not a pregnancy
I would suggest you to reconsult her Gynaecologist and she will advise the needful.
For future if you need contraception
discuss with your Gynaecologist and she shall prescribe your wife a regular contraceptive pill which will give her protection from getting pregnant as well as keep her periods regular.