If you have no evidence to prove that your wife has been living in adultery, then you cannot seek divorce. Past relations with a boy do not give you a right to get divorce. According to Section 13 of the Hindu marriage Act, 1955 you have to prove adultery of your wife which she committed after marriage.
You want divorce in the hypothetical situation which is not acceptable. You should refrain from making false allegation against your wife. Physical relation with a person before the marriage does not constitute matrimonial crime or infidelity. It shall not constitute a ground for divorce.
Infidelity, in the context of marriage, is generally considered a breach of trust and fidelity to one’s spouse. Matrimonial issues related to infidelity are primarily matters of personal ethics, morality, and civil law rather than criminal law. In cases of infidelity, the legal consequences typically revolve around civil matters such as divorce.
Under Section 13 of the Hindu Marriage Act, 1955, there are several grounds on which either spouse can seek a divorce from a marriage solemnized under the Hindu religion. These grounds include instances where one party has committed adultery, among others.
Section 13(1)(i): This clause states that a marriage can be dissolved if, after the solemnization of the marriage, either party has had voluntary sexual intercourse with any person other than their spouse. In other words, if one spouse engages in extramarital affairs or adultery, the other spouse may file for divorce on this ground.
Thus it is evident that for the adultery the wife must have sexual relations with a person other than spouse. If sexual relations were established before the marriage, that will not constitute adultery.