What does なってる mean?


Can anyone tell me what this means? The only definition I could find was
"summer vacation" which made no sense in the context. This is what's on ether
side of it:

> これ完全にマウン卜ポジシヨンに **なってる** から!




> nounになってる = nounになっている  
>  has become noun

You need to be careful to distinguish between the large and small characters.
It's なってる not なつてる and ポジション = "position", not ポジシヨン.

I have no idea what a "mount position" is, but it (これ）has become one.
Hopefully you can figure that out from the context of the story.

