Mazal tov on your upcoming wedding!
We’re sorry, but it would not be permitted to immerse with hair extensions. Laws about
chatzitzot (barriers to immersion) are especially stringent when it comes to hair. It is permissible to immerse up to
four days before your wedding and, for a kallah, even during the day. Perhaps you could get extensions put in at that point, after your immersion. Please note, however, that you would have to get them removed again prior to your next immersion.