I used to do the exact same thing, but as I've been getting more comfortable, I've shifted my weight more towards the front. An instructor told me that when you are leaning back, it's because you are mainly nervous. From what I know, it would be a good habit to break.
I'm used to going fast on skis, so once I started getting down some control on a board, the speed started to pickup, and so did the control. Can't explain it, but it worked for me. Been snowboarding a whole 2 times, and the first day I had to focus on it, the second time, I didn't focus on it so much. One trick that did help me, instead of focusing on putting your weight on your front foot, try taking some weight off your back foot. Don't know if it will work for everyone, but it helped me out.