Not that i'm an expert but i have sold a couple of paintings and things in my time...i'm not shooting you down i'm giving you free advice. The dude who said you should refrain from using the pc was correct, mess around with it but dont try and refine your technique with it, it will only slow you down for now.
Get an anatomy book and copy it, draw each and every picture in that book, if you can get one specifically meant for artists i would recommend using that.
I mention this because i notice you have the same problem i used to have and thats per portions!! They are a right bastard to master but once you got them under your knee you wont believe how it will improve the quality of your work.
What works for me is when i'm sketching from a model or reference picture i dont draw what i think i'm seeing, draw the lines and only the lines, its a difficult concept to get your head around, i'm having some difficulty explaining this idea to you by just typing. When you draw a tree for example or what ever, dont think "ok i'm drawing a tree, a tree looks like this etc etc etc" draw what you SEE, follow the lines. The same goes for lighting, lighting can make or break your piece. Light is just lighter and darker lines. Everything is about lines and placing colours in the right places.
The most important piece of advice anyone can give you and i'm sure everyone here will agree, is DRAW DRAW DRAW DRAW DRAW DRAW untill you get SICK and then draw some more. That is the only way anyone can improve. Be creative, keep painting, drawing, sculpting what ever tickles your nasty and dont let anyone shoot your work down ever!
I can see you have a natural flare for art but you HAVE to work work work work!!!!
Keep drawing and keep shining!!
PS. the budgie is cool :-D
"We question pictures before listening to them, we question them at random. And we are astonished when the reply we had expected is not forthcoming." Paul Rouge