Disappointed with nub theory guesses

I have had about 2 boy guesses and the rest girl. I don't even know why I feel so disappointed because I didn't care if it was a boy or girl at first. I don't think it's the fact that it's a girl, I think it's because so many have said girl so now I'm convinced and don't feel excited to find out. Because I feel that I already know. If I heard the words boy next week it would be a complete shock and I would feel like I've got to experience the excitement of finding out. I had a clear nub shot at 13 weeks, is there still a change it could have changed and it's a boy?