I would agree that some people are gifted, or natural runners and some aren't. I happen to really have to work at running, but I find I get a huge amount of satisfaction from simply sticking with something that is so challenging. I went for an 8 mile run last Saturday, finished feeling strong, and I was smiling all day. Who knew I could do it? Not me!

My heartrate also tends to be higher than it should be, especially at the start of a run, but it comes down as I get into it and after a mile or two it's usually fine. I run/walk the first few miles and find that helps immensely.

I'm also fairly slow (12 min miles), and right now that doesn't bother me because I am focusing on be able to complete a half marathon and besides that, well I'm just so delighted to actually be jogging any amount of distance that I don't care how long it takes me

If I were to be working on my speed I would start doing some track workouts and some hills too. Have you tried either of those? For your body to go faster, it has to practice that faster speed, if only for a limited amount of time.