How can one repent from recurring sins, given that the questioner's fiancé is the cause, despite her wearing a hijab? And is it obligatory to annul the engagement despite the wedding being near and the mutual love?

The matter is not about someone who helps one obey or desist from sin, but rather about the person themselves. You must reform yourself to be a cause for the reform of your husband and your offspring. Breaking off the engagement is not a solution; rather, sincere repentance is the solution, and you can combine it with a beloved husband. Repentance from sins is immediately obligatory by scholarly consensus, and it involves regretting the past, immediately ceasing the sin, and resolving not to return to it. If a person returns to sin after sincere repentance, their previous repentance is not invalidated, and they must repent from the new sin. One should not tire of seeking forgiveness and repenting whenever they sin. They should cooperate with their fiancé in obedience and avoiding sin, and increase the remembrance of Allah, supplications, supererogatory prayers, and invocations. If the sin involves transgressions between the engaged couple, it is recommended to hasten the marriage contract.