Increased Aggression - please help!

I have a ball python (Hercules) that I have had for about 10 years now. He has never shown any signs of aggression towards me in the past 10 years, no problems at all. I regularly held him and he never bit me/struck at me and very very rarely hissed. Within the past month he has bit me a few times and strikes whenever I open his cage. His appetite has also skyrocketed. He used to be a finicky eater now he will eat everything all the time. Im confused at the sudden change of behavior. I have heard from a pet store that sometimes older ball pythons just get aggressive, but I'm still concerned. My thoughts include not feeding him enough/large enough prey, not a big enough cage, not handling him enough? But again, nothing has changed recently that I could connect with the sudden increase in aggression. Any ideas from other long term owners or similar experiences?
Thanks
Sandra

you seem worried about food, what are you feeding, how often and what does the animal weigh...

1 medium rat 1-2x a week LATELY. 3 small mice have been substituted for the rat when pet store is out of rats (pretty often)
I dont know his exact weight. He's about 5ft long, and he's a big boy.