Ouch...running a half marathon in 5 weeks :)

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I have slacked a little in the last month (ok....alot). I only ran twice and I gained 6lbs back. I was/am on a training plan for a half marathon Sept 18th. I am trying to play "catch up" and tried to do 8 miles this morning. I did "jog" the first 6.5 miles, then walked/ran the next mile and practically crawled the last half mile. It was not the cardiovascular component that killed me, it was ligament pain in my left hip, a weak/tight feeling on the outside of my right knee and then finally right ankle pain the last mile. I'm sure the neighbors were laughing at me gimp the final stretch.

So here is my question....I go realize that I have gained 6lbs which doesn't help (I am not 170lbs and 5'4" - female), but is there anything I can do to strengthen those areas in the next 5 weeks? It is mostly muscle an ligament. I am ok afterwords and on the days "off" from running. And yes, I do stretch.

I already paid for the half marathon.