What is the religious ruling concerning marriage to a young man who has proposed to me, knowing that I have repented from a past full of sins, and I do not want to inform him of the details of this past? Should I accept him without informing him, or should I confess to him what I have done, given my intense fear of him knowing my past due to my bad reputation in my small town?

Do not tell the suitor or anyone else about the sins you have committed. Conceal your sins, as concealment is obligatory for a Muslim, both regarding themselves and others. As long as you are repentant, rejoice in the acceptance of your repentance, for repentance erases what came before it. Allah loves those who repent, and He transforms their evil deeds into good ones. Increase in the remembrance of Allah and in supplication to Him.