Search Results: lying about having a girlfriend

Incase you don't get my question. Let's say you and your girlfriend were on a break, then were on the road to getting back together when suddenly you start fighting and end it for good (your girlfriend tells you I'm done with you get out etc, tells you that you're no longer together). The next day you find yourself super drunk and hooking up with an old hookup. After this, you realize you want your girlfriend back and that you should've just worked out your problems. Do you tell her what you did while you were broken up? Or not say a word in the hopes that you have a chance of getting back together. Also if you're not young, put yourself in a 19 year olds place (aka not so mature). I'm asking because my boyfriend lied to me about this for an entire year. Then he finally admitted it to me. I understand we weren't together and immature and it's been so long and he's a changed guy, but I'm having a hard time accepting that he lied to me ( I did ask him multiple times before and he always said nothing happened). I know he was scared and knew he made a mistake and changed after that incident for the better and has never had contact with that girl again but that's not important to me, just the lying.