Congratulations on getting through the first six weeks of the program. That alone is quite an accomplishment!
As far as your speed, the short answer is not to worry about it. If you take a closer look at the program, you're supposed to run for a certain amount of time OR a certain distance. You're not expected to run that distance IN that time. In truth, that would put you at a 9:40 min/mile pace, and that's probably not feasible for most folks who are just getting off the couch.
Since you're working towards a specific 5k, I'd focus on the distance side of things and ignore the time from this point on. In fact, that's exactly what I did when I completed the program. I ran the first six weeks using the time intervals, then did the last three weeks using distance. That gave me the "mileage confidence" to run the entire 5k a bit less than a month later.
There's no "right" speed for the program except for the one that keeps you being active. Don't worry about where you finish, just focus on finishing. After you have a baseline performance (Personal Record, or PR), you can start to work at improving your times. Focusing on speed right now is an invitation to injury.
Finally, you'll have good days and bad days. Some days I get out the door and I struggle to hold a 10:00 min/mile pace. Other days I can cruise around the neighborhood at 8:30 min/mile and feel like I have plenty in the tank to go even faster. Don't let one or a couple of workouts dictate how you feel about your progress. Look at the overall trend. Are you fitter than you were seven weeks ago? I'd wager yes. 
Good luck with the rest of the program and with your 5k next month. Please keep us posted on how you're doing and how the race goes.
Don
"Don't fear moving slowly forward ... fear standing still" - Kathleen Harris
"Last is just the slowest winner." - C. Hunter Boyd