You need to do some serious study on animal form. Look at the bone and muscular structure of what you want to draw. Study it, breathe it until you can't stand it anymore. They say that if you draw something a hundred times, you've barely scratched the surface, but you at least have a good idea of where you're going. This is my advice to you.
Take a pencil and some paper. Draw everything around you. Every day. Make an effort to fill one large sketchbook page with as many different things as you can. When you've filled one sketchbook, put it aside, get another one, and do the same thing. Once you've reached the end of that, go back to your first book, and look at the progress you've made. You'll be surprised what you've learned.
I'm not going to just say your stuff is pretty bad without giving you some advice to fix it, but I will tell you that even looking up tutorials on deviantart will greatly help you. If you have problems drawing with a mouse, ditch the mouse. A pencil and paper is, and always will be your best friend.
I want you to save these drawings, and one day look back at them. If you do what I've said, redraw them in a few months time. You'll see what I mean.