Problem 1: I never have a problem with my shins hurting when I march, but for some reason, they really hurt if we're just standing still. And I've tried everything I personally know. We don't stand at attention all the time. And I do stretch. So I can't figure out why this is happening, especially seeing as I'm just standing there.

Problem 2: Also, I'm not sure about this one... after a long day of marching, my left hip joint hurts. Not any muscle... the joint. And I've checked to see if maybe I'm marching weird or if my harness is effecting that, but neither are the case.

The two things I've asked people about and no one seems to understand them either. Help!

Problem 1 - Consider shin splints. http://www.emedicinehealth.com/shin_splints/article_em.htm

Problem 2 - Sounds like bursitis where the bursa (aka a nifty fluid-filled sac that prevents friction) in your left hip joint is inflamed. Another article for your enjoyment -
http://www.emedicinehealth.com/bursitis/article_em.htm

Anyway, those are my first impressions from your descriptions. I'd need more information about the pain to have a better guess.