Your style is nice, and you have good confidence in many places. For example, on your very second picture, I like how you just put the third layer of shadow on the hands as a stroke, without trying to blend or blur them. The shading for the shoes on that picture are also very nice.
Currently, the lines do kind of detract. Don't write it off as "expressive", though. It looks like you really lineart your work, and so you should keep working on your lines. They can really make or break a picture. And even expressive (or sketchy) works can (and usually do) have clean lines.
Example.You can clearly see the sketch underneath it, and it's far from what you would call "crisp," but the lines are still quite clean.
My suggestion is to work on a bigger canvas and use a smaller brush. Even with the lineart capabilities in your program (assuming you're using the best settings - and those are the best I've been able to get with Photoshop - is that what you're using?) a tiny brush on a huge canvas will help make your stuff look crisp. As well, for ends of hair and flyaways, especially in the first three pics, taper your lines with an eraser tool so it ends in a point.
A last point: Shade to the edge of your line. Don't be afraid to go outside the line when you're doing the base layer, and then erasing the excess. And don't shy away from hard brushes. In fact, just for fun, try doing something using only hard brushes, and varying just opacity (and flow if you're in Photoshop). I think you could get quite interesting results.
What style are you going for? I quite like your chibi-ish style, even though it seems you want to expand into more realistic anatomy. I honestly commend you for resisting the urge to blur everything together. It creates a neat effect that I really like! This confidence can go a really, really long way! I wish you luck on your search for a mentor to suit your needs.!
