Running...on empty?

So I've begun week 5 of my half-marathon training. And I feel like I haven't made much progress. But when I put the facts together, I have. I just put a lot on myself to succeed and succeed well at everything I do.
Why do I not feel like I haven't made any progress? I'm not able to run too long distances at one time without stopping to walk. Inside a gym on a treadmill, I can do at least 4-6 miles running at a 6.0 or 6.5 mile-per-hour pace before I stop to walk. Outside, I try to do at least half of my route before I stop to walk. So far, it's been 2-2.5 miles before I stop to walk, usually running at the same pace as I would on the treadmill.
But when I really think about it, I HAVE made progress. I've stuck by my training routine, which is working out 6 days a week, four of those include running. I started "running" when I was a freshman in high school 8 years ago. I would only do about 1.2 miles around my neighborhood about once a week, if that. Then I progressed to five miles a week my junior year. I only remember running 3 miles without stopping once. Then I entered myself in my first 5K - the Race For The Cure in October 2003. For the next couple of years I would run off and on but wouldn't make it a good habit. In 2004 I was asked to be a lifeguard on a college internship so I spent that summer swimming and training for that. Then in 2005, I tried the Race For The Cure again. A few weeks later, I completed my first 10K. A co-worker of mine invited me to do a Turkey Trot that Thanksgiving. She and I bonded over running, and she sort of became my inspiration - that girl was in shape and so energetic. She gave me some running brochures, and I decided on a whim and to make it a goal to run a half marathon this year. The months passed and I kept telling myself to get my butt into the gym, but the half-marathon still seemed a good distance in time away. Finally, it was three months away. If I wanted to prevent injury and approach this half marathon in a healthy way, I had to train properly. So for the past 5-6 weeks, I've put my butt on that treadmill (not literally) and put myself through all this. Don't get me wrong - I love to run. But it's almost like I hate it at the same time, because it's tough and exhausting. But when I've accomplished my running goal for the day, I feel so ful-filled. It's a goal worth working for.
Unfortunately, I haven't lost weight. But I think, fortunately, I have lost fat weight. Fat weighs less than muscles, and I've gained muscle, so that's why I haven't lost weight. I've read so many times that it's not what the scale reads, but how you look and feel about yourself. I'm feeling accomplished.
I hate to cut this short, but I have to wash my mint julep face mask off before the power goes out. There's a huge thunderstorm rolling in and I have to get all my night duties done before the power goes out, if it does.
Maybe I'll be able to elaborate more on my "running" thoughts later...