Has he lost weight? If not, I wouldn't worry about it. If they're not losing weight or appear otherwise unhealthy, they can safely go much longer than 5 months without food, so there is a possibility you are in for a long wait.
Breeding season is one big reason they go off food. That's normal and happens to everyone.
I would just keep checking his weight. If his environment is good (temps, humidity, etc), and he's not losing much weight, there's nothing you can do except be patient and wait til the day he decides it's time to eat again.