Betta Fish: Is this an infection?

It's not fuzzy, just a swollen white cloud on his left pelvic fin. He's been very lethargic, only moving to sit in a new spot. When he swims he doesn't use his tail, just his pectoral fins. He's only interested in food about half of the times I try to feed him. He's been behaving this way for the past two or three days, the last picture is a full tank shot and how he normally has his fins displayed.