This is one of the dumbest expressions to come out of our language discourse in generations — including the urban version, "y'know what I'm say'n?"
I hate to imagine how it started; but when somebody is talking to me and he/she peppers the story with "y'know what I mean?"…I turn them off.
If I don't know what they mean, there is a BIG problem with their story.
They always blither-on and constantly say, "y'know what I mean?" or "y'know what I'm say'n?".
Of course, I'm not sure that they aren't convinced of my understanding; but rather they're using the lame phrase as verbal punctuation. Maybe this has some ethnic source, political correctness aside.
When somebody can't say WHAT THEY MEAN in simple terms, they should probably go back to elementary school where they can get remedial help.