regurgitated rat please help!!

[bstein54]

My argentine boa is 5.5 feet and has been refusing his normal frozen thawed medium/large rat for 3 weeks, he goes up to it for a minute or 2 and then backs off. Today I gave him a medium live one and after it went by his head several times he grabbed it. After he swallowed it and and it was resting down in his stomach for a few minutes he opened his mouth really wide and began squirming and forcing the rat up until it was out of him. I don't know why he is acting this way, he's always had a great feeding response. If you have any insight please respond I'm wicked worried about him.

Thank you.