Six weeks isn't a long time. In a few months, you'll develop some muscle tone, and the legs will stop hurting.

Maybe you should try going as fast as you can every other day. If you can improve your times, that will be a good thing. And if not, it will at least be amusing.

For drinks, try various types of Chinese tea which have no sugar yet are flavorful. They're pretty much calorie-free. Remember, it takes a long time to acquire a taste for a new beverage, so don't discard a flavor after just one drink. Also, try diluted fruit juice. Regular strength fruit juice has tons of sugar. Yes, it has nutrition, but the sugar is a lot. Man isn't meant to drink a ton of juice a day.