I really like your sketches a lot. I think more than your digital painting work. I find that in your digital paintings, you are mainly use local colors to paint. Try mixing it up a little to bring more dimension in them. I'm also noticing you are using white for your highlights. You should try to avoid it because it'll make the color flat. I would also suggest doing some value studies or do a black and white painting to understand how value works when painting.
You have a quirky style that I like but try pushing the values in your digital paintings more.