I don't know what is wrong with my Betta...

[Asho1387]

This is the first time I have ever had a Betta fish and I really think he is sick. His stomach is swollen and he is swimming really sporadically down to the bottom. He then just floats at the top and doesn't move (it looks like he is dead). But then he swims around aggressively again and it just repeats. Also, the scales on his face are very pale and look like they are flaking off. I'm really not sure what is wrong...please help!!

-I have him in a 1.5 gallon tank by himself and I only feed him once a day. The tank does have a filter, no live plants.