RainyDayRun,
I hope that you got a handle on your pace problem. I want to talk about building "speed". Can we say "getting just a little bit faster"?
Michael made some good points, but as he said,everyone is different. For starters, I doubt that you can do 1/4 mile sprints. Am I wrong? Forgive me if I assume too much; I only know what I was capable of when I could run the distance and time that you mentioned.
I tried sprinting the straight-ways on a track and walking around the curve. That seemed to be doing its job until I landed wrong once while slowing down. It took a few months for the dull ache in my ankle to go away.
Another way to accomplish the same thing is to find a hill and run up it at a good pace. Pick a short climb at first, a short hill or part way up a longer one. You don't want to sprint up, but go at a quick pace. You want to repeat the climb maybe 3 times. And that's why the hill should be short at first; you don't want to be gassed after one trip.
Take it easy going down! It's okay to walk or jog easy. Just be sure to take care of your joints.
Like Michael said, do not do hills and a long run on the same day. Run the hill one day a week. I park the car far enough from my hill that I can get warmed and loosened up before the first climb, then I have an easy run back to the car to stretch out a bit.
When running the hill 3 times seems "easy" enough, try to do it 5 times. After that find a longer hill.
This has worked well for me. The long runs build endurance and hills (speed work) increase speed. You can work on both.
Kim921, I recommend this workout for you. Use your hill the same way. Keep on conquering that beast on your long runs, but mingle in some hill work. Use half or 1/3 of that hill as I described.
This workout will be a lot shorter time-wise than a run. But it is great for your quads, which will help both endurance and speed.
[If you have not been running long or cannot sustain a 20 minute run, then I suggest that you really do build endurance first. This can stress your ticker. You don't want to hurt something by pushing your body beyond what it can do right now.]
Good luck! Stay well. And, take care of your joints!