Do you have any pictures, it could be the beginnings of fin rot or it could just be his coloring coming in.
The leaning and flips could be that hes just a weird fish, or he could have something more serious like SBD. If I were you I would not feed him for 1 maybe 2 days and see if he gets better, if not then its probably not SBD, just to narrow your options a bit. Maybe instead of feeding 4-5 pellets at once try feeding 2-3 two times a day.
Also the face blowing up is probably just him flaring, this is perfectly normal,bettas doit when they are fighting, breeding, see their reflection, or if they are just bored and feel like it. It probably looked like this: