Why I can't export in fbx my model? This is my model. I'm trying to create a skyscraper

Now in edit mode is this one:

As you can see the many polygons creating my model are also into the skyscraper, i.e. they don't finish on the surface of my model but they continue inside it. This is because i create many polygons that i combine each other to create a bigger model. In the end i simply unified all meshes in one with CTRL + J. Then inside my model there are vertices, faces and edges.
The problem is this one: i have tried to export my model in fbx and this is the result:

Why I can't export in fbx my model?
EDIT FILE BLEND
You may want to reconsider your modeling method as it produces lots of unnecessary geometry, face intersections, and fragmented mesh with no flow.

There is no easy one-button press to clean it up quickly, but you could try the new Edit Mode Boolean operations in Blender 2.77.

By selecting one of your "shards" (a complete chunk of connected faces or geometry) and pressing Space bar and Searching for Intersect or Boolean you could let blender try and detect all intersections and cut geometry accordingly. You can then easily erase all surplus geometry by hand and repeat operation for all remaining independent chunks.