What Could Be Wrong With My Horse?

My horse has got me stumped. He is an 11 year old Fjord Gelding. He is very sensitive and sweet natured. He loves his treats and grain, hay is in his opinion "eh okay". Yesterdy I got a call from the barn owner telling me my horse was laying down and not jumping up like usual when he see's people. He would eventually get up when you told him to. I took him, lunged him a little and there was no sign of lameness. All 4 feet were hot at first and then I came back 3 hours later and it was just the two fronts. He had no appetite for hay, only grain and his treats. Today, he wasn't obbessed with laying down, he was nibbling at his food (ate gr at turnout), pooped/peed, ate some bran mash (slowly), feet were no longer hot and not bloated. I gave him a handful of alfalfa mix hay and he ate it happily, I put some in his stall and he ate it, but about 30 minutes later went back to standing in the middle of his stall. When I came back to him to say hello, he started eating again. Once again theres no lameness, no heat in the feet.. just not too excited about eating/drinking, cantering on the lunge line (trotted fine), he's apooping/gy/pees and just seems a little depressed. One thing I havent done is taken his temp, I had to go buy one and will take it tonight. Any idea what could be the problem? I've already though about colic and laminitis but the signs dont make sense. Please be nice to me, i'm just curious if anybody else has seent his before.