Betta Fish: New betta owner!

I just got my Betta recently, he was a little wonky in the store when purchased (only floated at the top of his cup and could only swim on his side). He’s getting better at swimming but still floats when he isn’t sitting underneath something (like his plants or log). Any idea on what may be wrong with him? I’ve also noticed possible bloating and a crooked spine… (Also I ordered a new heater for the tank if temperature is a concern!)