hookup with ex while freshly dating someone else?

it was my ex boyfriends birthday yesturday and i have been seeing a new guy for the past 3 weeks and we just had sex for the first time on my ex’s birthday it was great. after i left i called my ex to wish him a happy birthday and ended up over there to hangout for a little and i wouldn’t let him kiss me and i didn’t want to have sex but he ended up giving me head and it was sooo goood. he deleted the messages and calls and i know he won’t tell anyone but he might bc he might be mad about the new guy. i really like the new guy and how things are going to desire and just comfortablity with my ex kinda ruined it. do i just keep this one a secret or???