It's pillow-shaded. For pixel art you'll basically always want the light to come from more of an angle. It makes any art more interesting but for pixel art it's important due to the color limitation as you'll end up with these highlight blobs centered within others. There's also what's called banding along the darker outline. It's probably mentioned in most pixel art tutorials, it might be a good idea to check some out.
I can tell you're probably already good at drawing non pixel-art and can capture a face fairly well so if you get these beginner mistakes sorted out I'm sure we'll see a big improvement in no time. : ) Actually the other pieces in your gallery are barely subject to these mistakes and already look good!
I'd also like you to dare using more contrasting colors for the skin.
Thank you so much! I'll definetly study that