It's taken me over a year to get much faster, but some of that was to do with confidence. For a while I was so concerned that I wouldn't be able to get to the end of whatever distance I was running that I made sure to take it easy, whether in training or when racing. It's only over the past couple of months that I've realised that I can up the pace a bit and still get to the end - and that's really made me feel good! If I'm training it's usually with others and we always run at chatting pace, but now I know that in a race (up to 5 miles, anyway) I can grit my teeth and go faster. (Not a lot faster, mind, I'm only talking 9/9.5min miles - Paula Radcliffe I ain't!)
Good luck, it will come in time. I think running consistently 3 or 4 times a week has been the key for me, it's helped me become strong enough to give it a bit more welly.