Whats wrong with my horse!?!?!?

I'm not sure whats wrong with my horse. He acts like he has a little tummy ache like he keeps nibbling at his stomach and his stomachs making ALOT of sounds. He isn't rolling or acting like he's in alot of pain, he isn't pawing or whinning. He does act droopy though. He's about 24 years old. I rode him saturday and he acted a little strange, he wouldnt run and just didn't want to go which isn't like him. Whats wrong with him? Dont tell me I'm a bad horse owner because I'm not, I love my horses more then anything. My dad has our other horse out right now and wont be back for a few hours. What could be wrong with him or is he fine? I dont think its Colic, some of my other horses have had Colic and he doesn't seem to be in that much pain.