Fish not very active, uninterested in food.

[Little Veiltail]

Hey guys, Geist has been acting strangely lately. He's never been a hyperactive fish, but lately he's just not moving much at all. Since last night he hasn't been interested in eating, and won't respond when I open the lid of his tank to feed him. He looks fine physically, so maybe he's bored of his food, or not feeling well for some reason. Here's some other info, and an image will be attached for reference. Thanks in advance.

Housing
What size is your tank? 3 Gallon
What temperature is your tank? 79
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes
What tank mates does your betta fish live with? None

Food
What type of food do you feed your betta fish? Aqua Culture Betta Pellets, sometimes Tetra Freeze Dried Bloodworms
How often do you feed your betta fish? Twice a day: 2 pellets in the morning and 1 or 2 in the evening.

Maintenance
How often do you perform a water change? Once a week, but I change the filter cartridge once a month
What percentage of the water do you change when you perform a water change? 50% every week, 100% every month
What type of additives do you add to the water when you perform a water change? Jungle Water Conditioner

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? Appears fine physically
How has your betta fish's behavior changed? Not very active, not responding to food. Floating near the surface on plants or behind filter.
When did you start noticing the symptoms? Earlier this week
Have you started treating your fish? If so, how? Added a bit of aquarium salt
Does your fish have any history of being ill? No
How old is your fish (approximately)? I bought him a little over a year ago.

[Little Veiltail]

Just gave him one or two bloodworms. He did eat those, which is a relief, but he still isn't moving around.

[Oldfishlady]

Its hard to tell but he looks a little bloated...is he? could you post a full body shot

I would start making some 50% daily water changes for 3-4 days and see if that won't perk him up and then with a 3g filtered tank I would do twice weekly 50% thereafter to maintain water quality

Hold food for 3 days and then offer half of what you normally feed and if he eat great..if not remove the food and try again later....limit the amount of the freeze dried food to 2-3 times a week as a treat-too much of the freeze dried foods can constipate them...but they are great for treats....

[Little Veiltail]

He's always been a very big fish, though now that you mention it he does seem like he might be too fat. And bloating might explain why he doesn't want to eat.

Just changed his water and now he's laying on the bottom of the tank. Hopefully he'll start to perk up soon. =/