Check your water quality today and see if there is any ammonia or nitrite. Even if he isn't eating, if you are adding food and the filter is not established, you will still get an ammonia reading from uneaten food in the tank.
Have you done any water changes since you got him?
Try doing a 75% water change and gravel clean the tank. Make sure any new water is free of chlorine/ chloramine before it goes into the tank.
Make sure the temperature is above 24 degrees Celsius.
If you don't have nay floating plants yet, add a couple of artificial plants and let them float on the surface.
When do you feed him, first thing in the morning, lunch time, night, when?
You want to let him wake up and spend several hours awake before feeding him. So don't feed him straight after turning the lights on or opening the curtains. Wait until lunch time or early afternoon so he has a chance to wake up.
Have you offered him any live food, brine shrimp, mozzie larvae, aphids, etc?
If not get some live brine shrimp from the local petshop and offer him a few of them.
Don't worry about him starving. He will not starve to death in a week. However, the fact he has not eaten after 6 days would suggest something is wrong with the tank, either water quality, temperature (which you recently corrected), or stress.
Make sure you don't have any soap, perfume, deodorant, grease, moisturising cream, or anything else on your hands when you feed him. This can contaminate the water and put strange smells on the food, which might discourage him from eating.
Make sure nobody is smoking, painting or using any sort of spray in the room.