Why don't you take picture of something like brick wall or bookshelf , in your pictures there is nothing in the middle of the frame, poor autofocus of your camera had no idea what is the subject of your pictures.
Without being picky... Nikon Nikkor AF-S 50 mm f/1.8G review - Image resolution - LensTip.com 2.8 isn't that great... 5.6/8 maybe. That being said, it's awfully cheap and just plain awful IQ wise.. The 1.4 version is very expensive, and not much better. If you want sharp wide open, leave Nikon standard primes alone.