am i wrong for being mad??

my fiancé who ive been with for 3 years and have a child with sent me a random video on snapchat today if a truck from a tv show and i guess forgot to turn the sound off on the video or accidentally sent it to me because he said “ i wish i could send this to *ex gf* we used to watch this shit” they were together for 4 years. she cheated and then left him cause she was unhappy and then we met shortly after. like very shortly. i didn’t know he had recently had a break up or i wouldn’t have been interested, but we met through mutual friends so i didn’t know him or her before some random day meeting. but anyways we’ve been together since, live together, have a baby, and are getting married next year. now i’m second guessing. my blood is fucking boiling, i’m hurt, confused, angry, upset, all of the emotions. so what do i do or say in this situation? i lost my fucking mind on him and he’s been profusely apologizing and saying he didn’t mean it and he doesn’t know what he said it and blah blah blah blah blah. what would y’all do?