bumping up my training for a longer sprint ?

First of all I am new to all this and started training only january of 2009, before that pretty much off the couch so to speak. since then quickly I got sucked into swim bike run.
I recently finished my first Tri with a distance of 400 yard swim, 8 mile bike, 3 mile run in a time of 1:03:51. i felt like i actually did pretty well for my first event except my run really dragged me down as i lost about 10 to 15 positions during that. i ended up 40th place out of 150 but i was strong in both swim and bike.

i have 2 more tri's coming up, one in 2.5 weeks which is a 600 yrd swim, 12 mile bike, 3 mile run
and the august one is 800 yrd swim, 15 mile bike, 4 mile run

the one i am concerned about is the august one mainly due to the extra mile run.

my training now is as follows

mon. swim with masters in the mornings 3000 meters in one hour
mon evening run 3 to 5 miles 

tues  spin class one hour

wed masters swim 3000 meters
wed night run 3 to 5 miles

thursdays rest typically if i can, occasionally i will do elliptical

friday morning swim masters 3000 meters

saturday 30 mile group bike up to 30 mph sprints, 3 mile run brick

sunday  up to 30 mile solo ride


i am wondering if i should be running more miles to help my run be strong enough to finish the race. my last and only race i had to stop like 6 times to walk a few steps due to my legs being shot. typically i can run no stops up to 5 miles and more but it didnt happen when i needed it in the race. really bummed me out alot to have to stop and walk. any suggestions? or is this typical when you do a first race? i wonder if it was just a pacing issue asi found it hard to pace myself on the run.