Betta Fish: Betta Fish acting weird idk what to do

Hi! Newish Betta owner. Peep has been acting weird the last few days and I'm worried. It first started with him hanging by the water intake and not moving from it to hold him up. Last night he was there and this morning he was also there until I turned off the water filter so he would come up for some food. He ate yesterday and I thought he was getting better but it looks like he's struggling again.

I did do a water change, checked the water levels for ammonia/nitrate etc and it's all clear. He has been using the decor around his tank to hold himself up or just the bottom of the tank. And today he isn't eating. Can anyone suggest what else to do?

I did put a bubbler in to add more oxygen in the tank, and I did the aquarium salt as my local fish store suggested it. I'm at a loss for next steps. The temperature is where it's suppose to be as well.

Thank you. Hopefully he gets better.