Husband [26M] is upset at me [22F]

Context:

A few weeks ago, my husband and I got into an argument which led to him telling me that I’ll finally get to be a single mom and to not ask him for help with our infant son. He emphasized to not ask him for help especially on Sundays because he goes to church and before I used to ask him for help. He never made good on that promise and still helps out but what he said bothered me. A couple Sundays ago I was taking care of our son when his dad had come home and I asked if his sister (whom we live with) was awake because I needed to do something. He questioned why I didn’t leave our son with him and I told him he explicitly told me not to bother him especially on Sundays. He said that I’ve changed my behavior since then so he’s open to helping out again.

Today:

It’s Sunday and my husband got home at 8 PM. We watched some tv together and then I told him I had to use the bathroom. I was holding it for a few hours because it was occupied then I fell asleep holding our son. I asked him to check if somebody was in the bathroom because I had to go very badly. I was still holding the sleeping baby so I didn’t want to risk checking myself. He checked and was gone for about 5 minutes. I texted him to ask him if somebody was in the bathroom and he didn’t respond. I got up and ended up waking up the baby so I just carried him to the bathroom with me. I barged in because I knew it was my husband inside and began to get ready to pee in the bathtub. He was in the middle of washing his hands and when he was done he told me to give him the baby. I told him it’s okay I just need him to get out. He started arguing with me and I just kept yelling at him to please get out because I’m already getting ready to pee. He kept trying to argue with me and I just kept telling him to leave so I can pee.

He got upset and said stuff like I was doing the most, he’s going to be the bigger person and be cordial, “let’s just let our relationship spiral downhill.” And all I could really say to him was “I don’t understand the problem I told you I really had to pee.” But he said that wasn’t his problem and that what I did was wrong. He also kept cutting me off and said he wasn’t talking about it anymore when I kept trying to explain. He said he doesn’t want an apology just for me to change my behavior.

Why is he so upset?