When I was in my early teens, if I would try to shout suddenly, my voice would unexpectedly come out as a squeak. It has never happened to me since then, so I assumed it might be something related to the change from a kid's voice to an adult's voice. It doesn't happen for women the way it does for men, but it happens to a slight extent. Maybe that's what is going on for you.
Hi, Jess, are you male or female?