Betta sinking headfirst and gasping

Hi all,
I've had my delta tail male betta for exactly one year today. He was maybe 9? months old when I got him. Yesterday he was fine, but today when I went to feed him we couldn't swim up. I lifted him up in the water because I thought he might be stuck in a plant and he immediately sunk head first down to the bottom, where he is now laying and gasping. He is in a filtered, heated and cycled 5 gallon tank that's been running since March of 2020, parameters 0,0,10 temperature 78F. I do water changes once a week and dose prime aquarium salt for his fin rot, but nothing changed between yesterday and today. Right now he's just laying on the substrate, gasping and not moving. He sometimes tries to move but can't move his head up.
Please help, he's had a lot of problems but I really really love this fish.

 

Here, try and fill out this Fish Emergency Template | Freshwater Fish Disease and Fish Health Forum | 376562
it’ll give us some more info so we can help a bit better. Could you attach pictures as well? does he seem bloated? If you look at him from above, do his scales kind of stick out to the side? Unusual red marks anywhere on him, especially by the gills?

 

Tank
What is the water volume of the tank? 5 gallons
How long has the tank been running? Since March 2020
Does it have a filter? Yes
Does it have a heater? Yes
What is the water temperature? 78 degrees F
What is the entire stocking of this tank? (Please list all fish and inverts.) Betta fish, nerite snail

Maintenance
How often do you change the water? Every week
How much of the water do you change? 50%
What do you use to treat your water? Seachem Prime
Do you vacuum the substrate or just the water? Substrate

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? API master test kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0
Nitrite: 0
Nitrate: 10
pH: 7.2

Feeding
How often do you feed your fish? Every day except for Sunday
How much do you feed your fish? 3-4 pellets
What brand of food do you feed your fish? Betta pellets and bloodworms
Do you feed frozen or freeze-dried foods? Freeze dried bloodworms

Illness & Symptoms
How long have you had this fish? One year today
How long ago did you first notice these symptoms? This morning
In a few words, can you explain the symptoms? He's sinking head first to the bottom, unable to lift his head up, and gasping at the water.
Have you started any treatment for the illness? No.
Was your fish physically ill or injured upon purchase? He had fin rot
How has its behavior and appearance changed, if at all? Some fin has grown back

Explain your emergency situation in detail. (Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now) He's sinking and gasping and I don't know what to do. There's no bloating or redness.


He's stopped gasping. I lifted him up to the surface to try to help him get oxygen through his labyrinth organ but he didn't do anything, didn't even flop around.
He's stopped moving at all, even when I touch him. I don't know if he's dead yet but it seems like he will be, very soon.

 

It could be a fungal or bacterial infection, he has all the symptoms.

 

Thanks for trying to help. I don't know how, but this came on really fast and he didn't make it. He seemed perfectly fins last night, but he is no longer moving at all or gasping. He's dead.

 

I’m so sorry

 

I'm sorry patterson.