my fish cant stay away from the top even though it tries to!

Question
I've been taking care of my friends beta fish for the week of spring break and at first the fish was just swimming everywhere all the time and was acting all sporadic. First for some reason there was a fine film of something on top of the tank with loads of little bubbles (it almost looked like a fine layer of ice, because it looked webbed, but it was a fine film), and the fish seemed fine  but it would freak out every time someone got near it (might just be a personality thing) Well i changed the water for it today. I put some water in a different cup added some stress coat drops and then put a little bit of the old water in with the new, transferred the fish and cleaned out the bowl...but I've noticed that for some reason the fish's belly is a little bit rounder than usual and every time he swims towards the bottom (because he is still very active)the moment he rests he floats to the top and kind of leans sideways. Did i maybe overfeed him accidentally, or does he have a swim bladder infection? and if so what would i do to make it better...maybe not feed him for a day or two? It just seems unusual to me and i want to make sure that the beta gets healthy again, especially since i feel horrible that he obviously wants to chill in the middle of the bowl or swim around the bottom for a bit but he keeps floating to the top every time he takes a pause! thank you so much!!!

Answer
Sounds like his bubble nest. Nothing to worry about - sometimes they may appear frothy. Also, it does indeed sound like SBD. Just give him 48 hours hours before you feed him again, and then give him a crushed shelled pea to help aid in digestion and he should be good as new.
In the future, remember he only needs a very tiny pinch twice a day - no more.