Guinea pigs

My male Guinea pig hasn't been eating much, or drinking much. Usually everyday I have to refill his water at least once, usually twice. His food bowl is still full. Every other day or every 2 days I have to clean out his cage because of how much he pees and poops. I cleaned his cage out early yesterday, and it's still spotless. Which is VERY odd.. He had snot under his nose real bad, never has that. He's shedding real bad, and looks a bit smaller. When he started making his squeaking noise he sounded sick. I went in there a few minutes ago and he was just Laying there, he came up to me when I gave him some lettuce. I let him out of his cage every day to run around and play on the floor. He got out of his cage and just laid there, very odd for him. I started crying because he just isn't being himself.. It worries me. Anyone know anything about Guinea pigs or have personal experiences?