Good morning.
The guppy does look like a male to me too. Too I don't see a
gravid spot. (dark area behind the anal fin) In most cases the gravid spot may indicate pregnancy. Did the swelling happen over night or a couple of nights? It would take a pregnant female longer than that to get that big.
Peas are a good suggestion just in case it is a male and it's constipated. Too you can feed the fish pre-soaked freeze dried daphnia to help it relieve itself. These too foods act as a laxative for fish.
To prep the peas....I use thawed, frozen peas, (canned peas usually contain salt so they aren't recommended) slice them in half and remove the skin. Then I slice them into sizes about the same size as one of the fishes eyes. It may take a feeding or two before it realizes that it's food. If it doesn't take the pea then fast the tank for 1 day and try again.
Best of luck and please keep us posted.
Ken