Possibly a combination of factors. First; what you posted is a very small file, so when a computer (any display) attempts to make it a decent size, it will look "pixelated", which means that you are seeing the individual pixels.
Another possibility is that the camera does not handle high ISO very well, so it creates "noise" which is an artifact of the signal-to-noise ratio coupled with the processor's ability (or inability) to display a clean image.
I understand your frustration, and given your overall knockout personal appearance, you should have a much better portrait.
1. Get a better camera.
2. get a better photographer.
3. save larger file sizes.