Really Strange Behaviour!

Hello. I hope someone can help me. My male budgie is 6years old and very tame! The last week he has been squeaking and going crazy in his cage. Running around the bottom, hanging upside down sometimes just by his beak just frantically trying to get out of the cage. When I open the cage door he literally falls out he's that's desperate to get out! He then flys straight into me and snuggles in my hair and falls asleep. If I try and and get him on my finger he hates it or even try to put him back in his cage. Don't get me wrong I love him being really friendly but I'm getting a bit worries now incase he thinks maybe I'm his mother etc and he doesn't eat as much as he used to and I'm scared that he will get to used to being warm next to me, and then be too cold on his own in his cage even though we cover his cage up. Can someone please explain what this strange behaviour is and if it's risky "mothering" him too much. Thank you.