Paranoid Or Sick Fish?

So my betta had been acting a little odd the past few days. He's resting strangely on the bottom. His head is up higher. He also seems to be swimming like this. Doesn't seem liķe swim bladder because he has no trouble going up or down. He also can't seem to flare properly. Only one side sort of flares out when before he'd full on flare at me in the same situation.

I'm worried because I bought another betta who had similar but much worse symptoms who died like 10 days after I got him. That was about a month ago.

He's still eating and zooming around but I don't want it to become something. Should I just maybe up water changes? Add aquarium salt?

Oh btw this is my mom's fish which I take care of. I'm still trying to talk her into a heater. No judgements.

 

getting a heater will help with your mothers sick betta, i recommend doing %15 water changes daily and see how that goes. what size tank is he currently in?

also some pictures will help if you can get some

 

He's just kind of sitting/swimming face up.

He let me get a better picture. It's just weird. He's never done this before a few days ago.

So I may or may not have this figured out. He just full on flared at me so that's good. He can't fit behind his filter where he use to hang out. So that may be why he's hanging out in weird places. Still thè way he's sitting is weird right?