Boyfriend living with me???

Hey guys, so I've been dating my boyfriend for 5 almost 6 years. We have been long distance this year and he might end up moving to the same city as me next year. The plan was that we would live together but the problem is my dad is either really naive or ignoring the fact that we have slept together (not just in the sexual sense but also in the actually sleeping in bed together). I'm so scared to tell him but my boyfriends mom has threatened to tell him herself if I don't. How should I go about it? Any advice is appreciated.

We also need him to move in with my roommates and I because the rent is going up and if he moves in with us we are going to be paying less than we are now 😂