Runner's Training Tips: Question about Training for Beginning Runner

I am training for an 8K race -- this is my first ever.  I am pretty fit as I have been working out with a trainer for 6 months and exercising 5 days a week -- however, I am about 40 pds overweight.

 

I have been training inside for about a month and can run 5 miles in 59-63 minutes on a treadmill.  I run very slow. I began running outside two weeks ago --  I have ran 3 miles the first week and 4 miles the second week.  Both were tough runs but I ran faster than I do on a treadmill.  On both of the runs, I stopped a couple of times for water, to catch breath etc...and the runs seemed pretty difficult especially the last mile. However, the next day I was not sore at all...except my knees which kind of always ache after I run.

I am most concerned that I have a little over 3 weeks before the race and am wondering what my best strategy is.... keep pushing on the mileage of running outside and my endurance will build up or should I stick to 4 miles until I've mastered that and then try to add a mile the last week or so. 

 My goal is to finish the race strong and not feel as if I'm being drug across the finish line.  Thanks for your input. 

I agree that focusing on mileage is the thing to do......however since you only have three weeks left and are targeting an 8k (roughly 5 mi).........I don't think you should do too much beyond 6 miles on a day.  Perhaps bump a few of your days up to 5 miles next week (keep other days down to 3 or 4).  Then the following week bump the longer days up to 6 miles.....and the others at 4.  Then you are one week away from the race and you want to rest up a bit.  You should take the longer days back down to 5 miles in the last week.