What others have said. However, what are your weekly mileage? There's a lot of speedwork you can do. Try for at least 4 runs a week at minimum (preferably up to 6.) On all but one, run at an easy pace. That includes your long run. On that one hard run per week: switch off between intervals and a tempo run. For intervals, I just start at 5x(3min hard/1min rest) and work my way up to 10 sets. Then for tempo, start out at 20 minutes and work up to 40. For paces, you can use the Jack Daniels pace formulas. There's a spreadsheet somewhere, but I don't use it because I utilize heart rate.