Hi Jacky, as has already been suggested it may be a good idea to have him checked-out. Try not to worry too much your baby is very young. My baby used to spend virtually all his time at the bottom of his cage - even sleeping there and has only recently stopped doing this (he is now 9 months old) but still occasionally explores there.
If I were you I'd offer as much variety of foods as possible including veggies, fruits, pellets and seeds, he will eat whatever takes his fancy. No bird in good health will starve himself. Try reducing the amount of food offered by hand and gradually phase this out. It sounds to me like he is only semi-weaned. Have you had him long? Is he is still getting used to a new environment?