Way to go! Keep going at your pace. A mile is a mile, doesn't matter how fast you do it. You're doing more than those who sit on the couch doing nothing.
I had to laugh at the speed walker comment, because yeah, I'm the same way sometimes. But one thing I've noticed out on our forest preserve trails, when I get passed by a faster runner, they're always encouraging "keep going, doing great".
I too find the first "start running" segment is always hardest, but then the subsequent sections get somewhat easier.