lovebird health!

i have a lovebird question too...

my lovebird benjamin has been missing some of the little feathers by one of his eyes for a couple months, but now the spot is getting bigger, and there are also little spots coming on the other side of his head. i know he rubs his head and face on his perches, so i assumed this is what it was from. he is behaving normally and gets vitamins. is there a way that i can get him to stop rubbing his face, or is there anything else i should be worrying about that could cause this? i'm worried that if he keeps rubbing where there are no feathers, he will injure himself.

a pet shop told me that maybe he is frustrated about being in his cage..but he gets to come out every day. i would appreciate any suggestions! thanks