“Dark Spot Behind the Lumineer”

I wanted to reshape my front (they was little bit short) teeth, so I decided to get lumineers about 3 years ago. They give me batter look, but they not impeccable ( little bit opaque ,not translucent as real teeth). But now I encountered with this problem with dark spot and guess it’s gonna be abig problem to eliminate it. Unfortunately this dentist isn’t available now.

Please , please help!!! I have done 8 lumineers on the top 3 years ago.Several days ago i've noticed the dark ( greyish)spot right behind the one of the front lumineer( tooth). I looked as close as possible to it and noticed it was not a surface mark... it was on the inside. I shined a flash light behind my tooth and you could REALLY see the dark spotpots on the tooth. It takes up the whole middle part of my front tooth... and when you look at the back of the tooth, the surface has no decay either. I was wondering if maybe the glue or something they used did something wrong? How i can get rid of it, now it looks horrible!!Dentist performed this is not available now.Help!