Lied about birthday to boyfriend
So when I first met my fiancée he asked when my birthday was. I estimated about 8 months. No big deal. So 8 months came around and we had already been dating for that long and my b day never came up. He asks what date ny b day is on and I say the 20th which is true. So he thought my b day is march 20 instead of June 20. We've been together for 2 years and I don't know how to tell him it's not in march. I'm scared a family member might slip before I decide to tell him or not. What should I do? Tell him or just leave it alone?