Boyfriend of 4+ years unsure of wanting to marry me.

This is my first time posting here or anywhere but I feel very alone right now and not comfortable talking to friends or family right now so I’d like outside advice and opinions. My (26F) boyfriend (29M) after four years admitted that he’s not ready to marry me. I purchased a house a couple years back and asked him to move in with me while he finishes school. The idea was that once he finishes school we were going to get married. (He graduates in a year)The only thing stopping us was his financial situation due to being a full time student. Recently I watched a dumb Netflix show revolving around partners not being ready to be married and as a joke I said “are you ready to marry me? “And to my surprise he admitted that he’s not ready not only financially but also he thinks that our difference in religion worries him as well as our communication during fights. I love this man and we have been together for 4+ years now. I am absolutely ready to marry him and I’m sure about us fixing our communication during fights. When it comes to religion though idk. I’m not religious at all and idk why he would only bring this up now. I know he has a very Christian upbringing but I never thought it would be an issue for us. I guess I feel like after all my weve been through he should know I’m the one for him the way I do. I guess I feel like that was the plan when I asked him to move in. Right now he is in finals and we agreed he’d go stay with his parents to decide if I’m what he wants after his semester is over. But meanwhile when he’s home everything is good. But when he leaves I can’t help but feel like I deserve a man that’s excited to marry me. Someone who doesn’t need to leave to think about it. Please any advice would really help.

TLDR: boyfriend of four years is suddenly unsure he wants to marry me and wants time to think about it. I’m unsure of how to feel or how often this happens to people.