Your forms aren't properly understood, so it looks fake, smooth, plasticky.
Do some studies of the human body and try to observe how the body translates to basic shapes. Spheres, cubes, cones, pyramids, cylinders, etc.
You should also study texture, and I don't mean brush texture to add senseless grain to your paintings. Learn how to manually paint finer texture to represent the materials you're trying to depict. Once you understand how the materials work, you can use a brush to shortcut the process.
I hope this helps!