Sudden aggression. Anyone know why?

Hi, my tegu is about 4 to 5 years old and it's a male. He used to eat every 2nd day however now he is always hungry and I feed him everyday. Every time I open his door he runs out with his mouth open ready to attack. I understand this is a feeding response but he latched on to my leg last week while I had him out with me. He's never done that before. Today we were sitting on the couch and he suddenly grabbed the pillow and kept shaking it around. He wouldn't let go for about a half hour. He's never been like this before. Not sure what has suddenly brought it on. He does have swollen gums on one side of his mouth and has a vet appt tmrw. Not sure of that has any relation. Any ideas?

I have a video but cant figure out how to post it from my iPhone.