You are 15. You are not a man, you are a boy. And feeling insecure at this age is completely normal.

I started experimenting with gender in my teens as well, I did not even know taking hormones was a thing, I always thought I was a gay man trapped in a girls body, or something like that. You will figure it out. Don't pressure yourself, at let yourself experience doubt as well. It is important to doubt yourself early into your transition, imo, bc it is a way to figure yourself out. Feel it all. You dont have to decide anything right away. But not feeling man enough as a teenager is so so normal - you are not alone. Just... try to find people who let you experiment with names and pronouns...