I'm guessing you're just doing long steady runs Dave? You need to mix up a bit with some core strength and intervals with a bit more intensity. If you're just on long steady runs you'll only be burning calories when you're actually running and you'll plateau - which it sounds like you have, mix the training up with higher intensity and a bit of core work and maybe a few weights and you'll charge your muscles and metabolism up more so you'll burn more calories during rest, should bring you onto the next level. See you sunday