It sounds like an infection. Maybe from a cut? Sorry I don't know what to do to help but he might be saved by antibiotics if he's not too weak already.
Just get him to the vet quick as you can and try to reduce stress. If he's not soaking you can try squirting him with water. He might benefit from a bath in clear unflavored Pedialyte since he hasn't been eating, but you don't want him to struggle and risk hurting his leg further.
What kind of water do you use? Distilled water can cause bloating, but it could also be caused by the infection or something else.