Sorry, I think this may come across as a bit rude, but I feel like you're falling into a trap I did when I was starting out. Try not to fall into a trap of drawing only heads! it will make it far more difficult down the line. I drew only heads and faces for a long time, and it really delayed my progress... I only draw as a hobby, and I'm really not that good - but you should try draw new things all the time, from reference. Think about what you're doing right now as writing the letter a over and over. While you'll get extremely good at writing the letter a, when it comes to communicating a full range of ideas, you're extremely limited. When you draw new things from reference, it's more about learning to recognise shapes, and then you can more easily think about how shapes interact, you'll understand how to do different poses and so on. Things like drawing hands is probably really difficult for you right now right? but this is because the hand is so complex, simply writing it from memory won't work, you have to understand how the shapes interact.
Sorry, perhaps this is a bit preachy... if you're interested in pursuing art further I suggest reading Drawing on the Right Side of the Brain. This book really helped me! You can find it pretty cheap used. The 2009 print is pretty good and easy to read, but I'm sure you can find it for free online too ;-)
I'm sorry! I know this is probably an annoying message, but I see a lot of my younger self in what you're doing... and I got really bummed out by my personal lack of progress back then... but at the same time you have so much to look forward to! if you stick with drawing for 5 years, you'll make so much progress you won't even believe it! agh... I sound like an old woman... ok good bye :x