you need to be sure to use the 1x1 pixel brush, as thicker brushes lay down large swaths of pixels that make your art more oekaki than pixel art. i'd start again, this time working with that smaller brush, on a much smaller canvas so you can manage the individual pixels much more easily

you've got the general anatomy down, but it looks like you used the non-AA brush tool with a tablet or something because of all the unfinished lines, like to the side of the head