YAY just stick with it and you'll get the speed up. When I did this last year we didn't even worry about speed until the last couple of weeks and I think we repeated a week in there somewhere. This is a great plan a year later and I'm still running!
I had to reschedule my C to 5K plan. I don't have a treadmill and it is just too icy to run outdoors right now. Hopefully in a few more weeks it will be dry enough for me to start.