Your frog is not well. These frogs eat every 2 days or so if they are feeling well and kept appropriately. IF it hasn't eaten in weeks it's likely on death's door at this point. In Pacman frogs, the most common cause of death is not keeping them at the appropriate temperature and humidity. This leads to lack of appetite and they fade away. I doubt there's much you can do for yours at this point but a trip to the vet is certainly in order. You also need to make sure you have the correct conditions for your frog, otherwise it won't get better either.
As for age, it's impossible to judge the age of these frogs accurately. Their growth rate is highly dependent on how warm they're kept and how often they're fed. The kind of food also has a bearing. If they are not fed well when young, their growth rate can be severely retarded, effectively stunting them. If yours recovers, it's likely in this situation.