Why get mad

So our son woke up at like 3am this morning and it was my boyfriend's turn to deal with him and he tried feeding him an old bottle I tell him it's old and he gets mad at me about it so after about an hour of dealing with him he wakes me up and was like you deal with him so I got up even tho it was his turn all he needed was a diaper change and more food I love my boyfriend but he frustrates me sometimes