What zone are you generally running in for your steady state/easy runs? I have a hard time running any easier than zone 3. I do my long and easy runs in zone 3 and tempo and track runs in the mid zone 4 to zone 5.
Most of your runs should be done at an intensity that you can repeat, day after day after day after day . . . . you get the picture. Many people over think this and/or get too worried looking at a HRM. Solid running base fitness and endurance comes from repeating more or less the same workouts, with a bit of stretch each week with the odd tempo run or harder effort, day in day out for several months.
My LTHR is around 171 for running, corresponding to the middle of Zn4. The majority of my mileage is done in Zn2 which for me should be 135-145 bpm although I rarely wear my HRM for these workouts. When I do though I find that I’m usually between 140 and 144. This is a pretty comfortable pace… slow enough to carry on a conversation.
How did you set your zones up? Unless it was through some kind of extended running time trial, you may have the wrong values for your zones. In any case, easy runs should be just that- easy runs and if you are running at a higher intensity for a large majority of your runs you are greatly increasing your chance for injury.
It sounds like you need to spend some time developing your aerobic system. Like what others have said, if you know LT HR for running shoot for running 25-30 beats below it. You may be runnning pretty slow for you at that HR (AeT) but as you develop your aerobic system better you will start to run faster at that same HR. Monitor your run pace at that HR (AeT) over time. Once it stops improving then it’s time to switch to higher intensities.