DH and I have been going through a hard time recently. Yesterday, we had a good night and something prompted him to say about there being only 2 people in a relationship. I said, 'yeah, unless there's 3', just trying to be sarcastic and correcting. I didn't mean about there being 3 in ours or anything, I was literally just trying to be irritating by being jokingly pedantic. He then went off in a big rant about how I shouldn't make jokes about sleeping with other people (?), about how I know he's got jealousy problems so why joke, and about how he thinks there's a chance I've been cheating on him recently, and then said (in front of our 2 year old!), 'if you did, I'd beat you up!' He didn't mean it literally, he was just scrambling for things to say, he's never laid a finger on me. I was more angry about him thinking it's okay to say stuff like that in front of our son!
He's apologised since and clarified he didn't mean it for a second... but AIBU to be so angry about this? I was doubting the relationship anyway.