There is a process for validating a marriage without the knowledge of the unwilling spouse, and you can ask your pastor about radical sanation if you wish (especially if what concerns you is receiving the sacraments of confession and Communion for yourself), but I don’t know if such a process could be completed before your niece’s confirmation. And, speaking personally, under ordinary circumstances I cannot recommend doing something your husband is opposed to without his knowledge. It would be far better for your relationship with him to be upfront with him about your need for your marriage to be recognized by your Church and persuade him to do so for love of you.
The fact is that confirmation sponsors need to be Catholics in good standing with the Church, which includes a valid marriage for those who are married. Your niece should have chosen someone else to be her confirmation sponsor, and very likely will have to do so if your husband refuses a convalidation. Rather than trying to find a way around the Church’s requirement that you be validly married, perhaps you should concentrate instead on rectifying your choice to marry outside the Church.
