If your 1 billion light years from earth, you are still effected by the Earth's gravity (well its likely smaller then experimental error but never mind that it still exist).

So there needs to be gravitons from Earth flooding the entire sphere of space for 1 billion light years around the Earth. All these gravitons have mass, and are emitting their own gravitons. Which all have mass and energy! Where is this mass and energy coming from? It really can't, it violates the laws of thermodynamics. But so does Dark Energy so who knows.