this seems like a big step forward for you, so congrats! I'd check out the anatomy changes that Fool recommended, they really help the shape (at least to my eyes). Also, something that was hard for me to learn but that I think you could really start practicing is to not be afraid of using larger pixel brushes than just the 1 pixel. It's hard to say for sure without seeing a WIP but it looks like you did some line art, and just started doing the high detail shading pass with a 1px brush right away. Take the extra time to grab a larger brush (on a pic this size, at least a 4x4 px brush) and paint in all your main values - roughly define your shape using only light and shadow. When it feels like a blossom without the hard edges and fine highlights then you know you have it right, then shrink down and start working in the finer details! This will help save you a lot of time, because things like Fool's anatomy changes will not require massive repaints; you'll be able to catch them when the piece is simpler.
Re: the dithering, you've done mainly a 50-50 pillowshaded dither, which doesn't read particularly well on the small, thin shapes you're using. It's making your surface look a little dirty or wormy. Notice that Helm started from a different base; some small shapes and some very large shapes, and the dithering is not used to soften the shapes but to join and smooth them into a single surface. For me at least it helps a lot to consider the end-goal of dithering, not just accomplishing it for the sake of dithering period. Helm's example provides a painterly, abstract background, not just a 'blur effect'. Think about how you want your background to look, and then think about how dithering might help you to accomplish that!