saddlesores nailed it.

Your knee pain is clearly from overuse ... likely aggrevated by an improper fit. Regular riding strengthens the knee joints (thickens tendons and ligaments), then specific touring training builds from there. You appear to have skipped those very important steps. You should halt the tour or drastically reduce the distance, either by shortening the route or covering some of the miles by some other means of transportation. If you must continue, please do as others have suggested ... gear down and spin, reduce daily miles, more rest days, ice every night, listen to your body. You can do real damage to your knee if you try to tough it out.