Is he slightly "bent" looking? Is he emaciated? Go to www.about.com and search freshwater fish disease to help isolate.

Try some live brine shrimp, my betta's love them. Probably not a long term solution but may get him back on track.

Is this a heated aquarium or a small aquarium or bowl? I see you live in PA. The cool weather in an unheated aquarium will make fish lathargic and slow metabolism. This would make him lay at the bottom and be uninterested in eating also.

He is in about a gallon bowl. It is not heated but the room temperature is a constant 73 degrees (thinking that the water temp would be the same). I was told by a friend that fish do get weird when the barametric pressure drops. Is that true?

Newbettaowner-
Bettas hail from southeast asia and prefer a temp closer to 80 degress. His lethargy and poor appetite is related to water temp as woeisme mentioned. Continue trying a variety of foods, he was likely raised on something other than what you are providing. Frozen adult brine shrimp or frozen beef heart would be a good alternative to live brine (don't want to spoil him). BTW, bettas have a normally short life span ~2 yrs. You may have an old one! Barometric pressure plays a role in fish behavoir/spawning- doubt this is his problem.

Thanks for all your help. He is slowly starting to eat the food i provide him. I have no doubt that he will be better. Thanks again.

Room temp and water temp will vary. Just like if you leave a glass of water out. In the winter it will stay cold or be colder than the room.