Lemme tell ya what's what. You know why you feel like you aren't improving? Because your TASTE in art, the thing that got you into drawing in the first place, is a big factor. You have a specific artstyle in mind when you're drawing. You know what you want your art to look like. You probably got artists you look up to in terms of artstyle, and you want your drawings to look like theirs. And since you ain't there yet, you look at your art and feel like you're never improving.
You know what you want your art to look like, and because it DOESN'T look like that right now, you feel like you're a bad artist, and you aren't improving. But you just gotta hang in there. Everyone starts at square one, and only through constant practice will you improve.