Rats, roaches, and feces found in my boyfriend's apartment.

I'm in a new relationship and I haven't been to my boyfriend's house until earlier today. He wasn't with me and he gave me a key to get in and grab his wallet to bring it to him for work. Turns out his home hasn't been cleaned in 5 MONTHS. His bathroom is covered in mold with dirt all over the walls and a mysterious stain on the mirrors. The kitchen is loaded with animals and it looks like hoarders have been living in there. His house smells like a dirty farm. I don't know how the hell he has been living so filthy without even attempting to clean up. This is all so shocking to me because he is a clean guy and is very well groomed. He always smells good and is very into health and lifestyle (eating healthy and loves to hit the gym)... I feel like I've been bamboozled. I haven't talked to him about the filth because I don't know what to say without offending him. What do I do?