Betta - Weird Behavior

Hello,
 
My Betta is somewhat lethargic, I mean he's not sitting at the bottom of the tank but he's not active (or outgoing), he prefers (mostly) to sit on top of a plastic region from the pump/filter system (calm water there and lower lightning), though he moves through the aquarium from time to time.
 
He doesn't seem to be aware of the surroundings, it's like he's a bit high, he ignores the ambient, moves a bit slowly and recently he doesn't seem to eat (I don't know if he ignores the food or doesn't see it).
 
Also I didn't see any feces from him (making or on the ground).
 
To sum up:
 - he's apathetic
 - doesn't eat
 - stays more at  the surface (but has no problem going at the bottom)
 - doesn't poop
 - no awareness?
 - he does not have raised scales
 
He has a varied diet:
- http/shop.sweetknowleaquatics.co.uk/Sera-Bettagran-Staple-Diet-10g
- http/www.tetra.net/en/en/aquaristik/tropical-fish/food/specific-food/tetra-betta
- http/www.amazon.co.uk/Tetra-Freshdelica-Bloodworm/dp/B009PN8IIE (fed only once)
 
I have him in the aquarium for almost 3 weeks, I did plenty of water changes and parameters are stable but he seemed more active at first.
I have attached pictures with him then and now.
 
What can I do to make his life better?
 
Thanks

In the first photo he looks a bit bloated.
 
 

 
 he prefers (mostly) to sit on top of a plastic region from the pump/filter system (calm water there and lower lightning),

Click to expand...

I wonder if the current and light are too bright.
 
I am not a fan of the food you are feeding him, New Life Spectrum or Omega one betta pellets are better for him.
 
When posting a request for help can you please include the following info

1. Water parameters. (ammonia, nitrate, nitrite, PH, temp', Hardness etc)
2. A full description of the fishes symptoms.
3. How often you do water changes and how much.
4. Any chemicals and treatments you add to the water.
5. What tank mates are in the tank.
6. Tank size.
7. Finally Have you recently added any new fish?

You may cut and paste the template below and submit in your post:

Request Help

Tank size:
pH:
ammonia:
nitrite:
nitrate:
kH:
gH:
tank temp: