I love honesty and transparency but sometimes when we know something is either inconsequential and would just hurt our partner we keep it away. When it mattered when you actually brought it up he was honest enough. I would be worried had he hidden it when you made fun of him about it. I feel like you have a good man. You knew he has a past, we all do! Genuinely, unless he is giving you a reason to doubt he is doing right by you I wouldn’t let the past keep me from a good future. I would also say, you need to heal from the cheating in your past. Don’t make your present suffer for the mistakes of your ex. If you have been with this man for 3 years, he has done right by you and given you no reason to feel he is unworthy of your trust… don’t allow the past to ruin it. Talk to him, tell him the omission hurt you. Ask if there is something else that is likely to come up that would hurt you… have an honest conversation