My (28F) boyfriend (32M) shouts at me during sex and I don't like it. How can I make him stop?

Ok so my boyfriend and I have been together three years and we were getting along great, excellent communication. Until the other day when we were having sex and he started shouting at me. I was really shocked and I asked him what was wrong. He continued shouting at me and later said that he was stressed at work. I told him he couldn't shout at me and he said he was sorry. When we had sex later in the week he did the same thing, shouting at the top of his lungs. I shouted back at him to stop and I got out of bed and walked out on him. Do you think he's having a mental breakdown? I really don't like being shouted at but I want to work through this problem. How can I talk to him about him shouting at me during sex without pushing him away further?