You need to learn some basic anatomy lessons, such as how many heads tall is a torso normally, or that the nipples are usually one head’s length from the chin, or that a foot is usually about the length of the head, and so on. There are many standard proportion ratios you need to know and memorize–all competent artists know them.
You also need to work on your understanding of values, form, and lighting, or else your work will look like it’s lit arbitrarily without any logic or aesthetic design.
And you need proper references. Don’t listen to all the idiots out there who seem to think that using no references is some kind of badge of honor. You will never see a truly proficient and respected artist say that–only the ones who haven’t quite figured out what being a professional artist really means will regurgitate that kind of ignorant misinformation.
If you’ve never been to the Art Techniques & Theories forum, I suggest you go and read the sticky threads–they will be of immense help to you in your artistic growth (the link is below in my signature).