At a previous confession, I seriously thought I committed the mortal sin of gluttony when so I confessed it. Now that I look back to how much I really ate and what gluttony truly means, I realize that I probably did not commmit this sin. This means I stated something untrue at a confession. Should I mention this at my upcoming confession, or should I disregard this and assume that God will just overlook it as an honest mistake?
Nah. You made the confession in good faith. The priest could have asked some clarifying questions to determine if it was mortal or not.
Leave it alone. God knows what you did, you confessed it, and you’re forgiven. Don’t start getting scrupulous.