It is mathematically possible, but you have to understand the maths. Even if you do understand the maths, it's difficult to get your head round. It's the space-time manifold that's expanding and the relative expansion is not limited to the speed of light. Weirdness ensues, for example non-conservation of energy.

http://math.ucr.edu/home/baez/physic...energy_gr.html
No-one knows how big the universe actually is, but measurements of its curvature seem to imply that it must be much bigger than its observable size.

http://atramateria.com/the-size-of-t...at-is-visible/
It might be infinite, or it might be finite but closed and not have an edge at all.

http://map.gsfc.nasa.gov/universe/uni_shape.html