Stretching It

I have been trying to stick to my schedule posted here. Unfortunately some problems have been holding me back. My hip flexor is bothering me again. I think I can fix it by stretching it more often. So what is my problem? Time.

I am a full time college student. I don't have much time to run. I need to do something with my schedule so I can have at least 2 hours every day to go from the idea of "oh I gotta go run" and taking a shower after running.
I was, however, impressed with myself by the distances I am still able to run even after a month off. I am trying a little harder than I used to, but 7 miles is really not that bad.

I was a little sore on day 3 of the schedule(7 miles, 7 miles, then 6 miles) but after the run I loosened up. I think my main problem is stretching and warming up. I should be spending more time doing that, but I feel like I am wasting my running time if I start out with a 15 minute stretch. Then again, what do I know.

I suppose today I will stretch thoroughly before I run and try to keep my form nice. I used to think I could just get out and go, but these longer distances are proving me wrong. What are your warmup routines?