Two Steps Back?

I’m beginning to wonder if I’ll even finish this marathon.  The doubts are circling inside my head, and they have been ever since my last run.  You see, on Sunday my girlfriend and I went for a three-mile run/walk.  It was supposed to be easy.  We started with a five-minute walk and then began running for four out of every five minutes thereafter.  The pace was slow, at about 11-minute miles.  Despite all the precautions (I’d also stretched beforehand), my knee started getting sore a little past the halfway point.  We slowed to a walk for a few minutes, then I decided to try running again.  We continued that cycle one or two more times until we were home.

The knee never hurt enough to warrant a full stop, and it seemed to recover fairly well along the way, but it never felt completely sound.  Afterward, and throughout the next day, it still felt a little off.  Not sore, just not quite right.  Even now, as I write this, I’m pausing to massage the affected area, just because I feel like I should whenever it crosses my mind.

My girlfriend suggested I visit a doctor, but I can’t see the point.  A doctor will only tell me what I already know: I need to rest.  Which begs the question: How can I possibly prepare for a marathon that’s less than five weeks away, when I’m resting, and when run/walking more than a couple of miles hurts my knee?  Do I just tough it out?  Do I just give up?  Will a strap help?  Do I rest all the way until race day and then see what how far I get?  Do I give in to the lady’s advice and see a doctor, because he might be able to give a specific diagnosis and recommend therapy?

I think I’ll try the strap first, and then go with the last option if that fails.  But I still have to wonder, would it be wise for me to just be a cheerleader during this race, and take a long rest before attempting a marathon next year instead?