Does he live at home with his parents? Is this really about stepping foot into his family home or is this about something bigger (i.e., his mom’s acceptance and approval and what that might mean for your long-term future)? Have you talked about your future together and what that might realistically look like as two people with different religions and backgrounds? Is there an expectation that you convert? It’s hard to tell how old you two are, but if you are thinking this is it for you, you can open up these conversations.
FWIW, I do think some people do have a sincere embarrassment of other people seeing how they live. Whether or not that’s the case here, IDK. I have one ex-bf who felt too embarrassed to take me to his dad’s house (his childhood house) because he wasn’t from a nice area, he was worried the house was messy, etc. It felt like a non-issue to me, though, since my then-bf didn’t live at home, I’d met his nuclear and extended family, etc.