Look at the side of the fish, there's a black spot. If it black spot has blue spots in it, it's a girl. Otherwise, he's a boy.
If he's eating and doesn't seem worried about it, just keep an eye on it but don't stress. If he's well coloured and seems to be healthy looking (rounded tummy, alert in the tank etc), it probably isn't worms. But even if it is worms, it probably wont hurt him too much. Add some salt if you're worried (make sure your other fishes will be ok with it first), or give him a salt bath. Salt fixes lots of things.