This is over a month late (I hope I'm still allowed to reply, I'm new here) but the side view is a whole two pixels shorter than the front view. You need to make the hair as fluffy as in your front sprite. But that's not all, I'm just not seeing the same hairstyle, so it looks like a completely different person. The hair shape's all round, which is not the same thing we're seeing from the other two sprites.

When you're really, really struggling a lot with this kind of sprite, I'd recommend first drawing different views of the head on paper, trying to think hard about the hairstyle as a three-dimensional object, exploring different angles. For example, what would those two prominent hair spikes look like when seen from another angle? I see the character has more hair spikes at the back; what would those look like when you look at it from the left or right? Then, when you're satisfied with the results, translate that into pixel art.

Here's my shot at improving ONLY the hair, though of course you're the one who knows how this hairstyle works so I might've gotten it wrong:

As for the body, looks like you forgot the jacket's collar... And from the side it's also hard to tell that the character has arms, maybe you should add some more definition to them. Additionally, it appears that the jacket is shorter from the side, thus giving you less space to work details in.

Also, the mirrored front sprite looks weird because it's not very symmetrical. This isn't a bad thing per se, depending on what you're going for. Your eyes and brain got used to seeing it non-mirrored. The color of the arms and the sides of the jacket look like mistakes to me, but the blue shirt underneath seems to be asymmetrical on purpose.