my head is full of english 这样说可以吗

I think you should say,"My mind is full of English."

"my head is full of english" does not make sense in English. You can say "my head is speaking English".

I am involved up to neck with english.

应该可以吧

是可以的，这并没有语法上的错误，还是一句不错的话哦！·_@