Like in the title, I wanted to say something like "I'm no longer that way, it was long long ago", so should it be "ages ago" or "ages before"? For some reason, the first instinct was "ages ago", then it is an "I have been......" pattern, somehow, I felt "ago" just doesn't fit here? Plzzzzz help
First things first: in this case, it's "ages ago." Using "before" seems to require some kind of extra information, e.g. "ages before I turned thirty."
Additionally, you should probably be using the past tense:
I went through that stage ages ago.
The present perfect (of which "have been" is an example) is used to express an unspecified time before the present. That's why "ages ago" didn't seem to mesh: because you were specifying the time. On the other hand, either of the following would work just fine, because the time remains unspecified.
I've been through that stage.
I've been through that stage many times.
Hope this helps.