Help what do i do with my cheep and silly lies?

I met a girl about a year ago and I told her a silly lie.we both fell in love and are now engeged to get married but I still havent told her the truth because im worried that it will end our relationship. Because she hates liers what do I do im so worried because i love her and i dont want to tell her at all in fear of what will happen but if i dont then it will get worse and she may find out her self.