Weird behavior

My fiancés been acting weird lately and this happens a couple times a month but I’m not sure why. He’ll be fine, happy involved(for him), sleep normal hours etc. then out of nowhere he’ll start staying up all night, not sleeping during the day, some irritation. Then he’ll sleep most of the day and night, high irritation, ready to bite heads off for the smallest things. We got a new puppy recently who I’m still trying to potty train, he peed on the couch and my fiancé said he’s leaving, that he’s not staying here tonight. This is just one of the many examples, last night he yelled at me because I was making pot roast and he said he doesn’t eat pot roast (he ate it). I have no idea what his problem is and when I ask him he doesn’t say anything. I’m walking on eggshells and get anxiety if he’s asleep and the kids are loud or if we don’t have ketchup for something he wants to eat. It’s ridiculous. We’ve been together for five years and this has just started within the last year or so. If you’ve made it this far thank you and any help is appreciated!