okay this is kinda personal, but im being serious so please answer seriosuly.

I am a sophmore in high school and have not started my period yet. I know that the blood comes out of the bigger hole in the vagina but does something have to break before it comes?
I mean because i have experiemented (dont ask) and have found that at some point about two inches inside the vagina there is just a wall and i cant go any farther.

Is this normal?
and what has to happen before my period starts?